dissenting, with whom LAY, Chief Judge, McMILLIAN, ARNOLD, and JOHN R. GIBSON, Circuit Judges, join.
Moreland is entitled to 150 days credit for the time he spent in custody at the Residential Services Community Treatment Center (Center). The denial of this sentence credit violates the language of the statute and the Constitution’s equal protection clause. I respectfully dissent.
Deference to Bureau of Prisons Policy Statement
This case is about the meaning of two words: official detention. According to Congress, defendants are entitled to sentence credit for the time they spent in “official detention” before their court-imposed sentence begins. Unlike this court, I do not believe that the term “official detention” is “ambiguous” or “abstruse[ ],” and I would not defer to the interpretation of the statute adopted by the Bureau of Prisons.
If the text of a statute is ambiguous and thus open to interpretation in some respects, “a degree of deference is granted to the agency, though a reviewing court need not accept an interpretation which is unreasonable.” National Railroad Passenger Corp. v. Boston & Maine Corp., - U.S. -, -, 112 S.Ct. 1394, 1401, 118 L.Ed.2d 52 (1992). Thus, the deference is not absolute and the reviewing court is the final authority on issues of statutory construction. If a court “ascertains that Congress had an intention on the precise question at issue, that intention is the law and must be given effect.” Chevron U.S.A. v. Natural Resource Defense Council, 467 U.S. 837, 843 n. 9, 104 S.Ct. 2778, 2781 n. 9, 81 L.Ed.2d 694 (1984).
The statute at issue here does not define the term “official detention.” Every undefined term, however, is not necessarily ambiguous. For example, even though official detention is not defined, one could not persuasively contend that the term “official detention” excludes time spent incarcerated in a county jail. We routinely construe the meaning of statutes when important terms are not defined, and the “ordinary and obvious meaning of the phrase is not to be lightly discounted.” INS v. Cardoza-Fonseca, 480 U.S. 421, 431, 107 S.Ct. 1207, 1213, 94 L.Ed.2d 434 (1987). Although the statute does not expressly indicate whether “official detention” encompasses custody in a halfway house, nothing in the statute or *664legislative history indicates that “official detention” should be construed narrowly or contrary to its “ordinary, contemporary, common meaning.” Perrin v. United States, 444 U.S. 37, 42, 100 S.Ct. 311, 314, 62 L.Ed.2d 199 (1979).
Legislative History and Plain Meaning of Official Detention
The legislative history of the statute is significant because it demonstrates that Congress has continually expanded the class of prisoners authorized to receive sentence credit for pretrial custody. At first, 18 U.S.C. 3568, the predecessor statute to the statute at issue here, did not allow credit for pretrial custody. Act of June 29, 1932, ch. 310, § 1, 47 Stat. 381 (1932). In 1960, Congress, amended § 3568 and provided that a person convicted of an offense subject to a mandatory minimum sentence be granted sentence credit for time spent in jail for want of bail. Act of Sept. 2, 1960, Pub.L. No. 86-691, § 1(a), 74 Stat. 738 (1960). In 1966, Congress further broadened the scope of section 3568 by providing that all sentenced prisoners receive sentence credit for “any days spent in custody in connection with the offense or acts for which sentence was imposed.”
As the Supreme Court recently noted, Congress again enlarged the class of defendants eligible to receive credit in 1984 when it replaced section 3568 with the current statute. See United States v. Wilson, - U.S. -, -, 112 S.Ct. 1351, 1356, 117 L.Ed.2d 593 (1992). At that time, Congress also replaced the term “custody” with “official detention.” See id. Although the legislative history states that Congress did not intend a different result by this change in language, the new language is at least more precise than the old. See Ramsey v. Brennan, 878 F.2d 995, 996 (7th Cir.1989) (construing former § 3568) (“[t]he word [custody] is a chameleon.”).
With this legislative guidance, I turn to the ordinary meaning of the words at issue. Official is something “prescribed or recognized as authorized.” Webster’s Ninth New Collegiate Dictionary at 820 (1986). Here, a court order required Moreland to stay at the Residential Services Community Treatment Center and to obey the Center’s rules. The Center acted as an agent of the criminal justice system, and the term “official” certainly applies to Robert Moreland’s 150 day stay. The ordinary definition of detention is a “period of temporary custody prior to disposition by a court,” see id. at 345, so Moreland’s custody, at the Center must also be considered “detention.”
Degree of Restraint on Moreland
The touchstone here is whether the degree of confinement or restraint provided by residence in a halfway house is sufficient to constitute custody within the meaning or intent of the statute.1 The Bureau of Prisons, to whom the majority defers, recognizes this focus. See BOP Program Statement 5880.24(5)(b)(5) (time spent in halfway house as a condition of bail or bond “is not creditable as jail time since the degree of restraint provided by residence ... is not sufficient restraint to constitute custody within the meaning or intent of 18 USC 3568”). The only question before us is whether Moreland was subject to the degree of restraint necessary to allow him sentence credit. All agree that an incarcerated individual is entitled to sentence credit, so it follows that a defendant subject to conditions as restrictive as incarceration may receive sentence credit. Under this standard, Moreland is entitled to sentence credit. Although the court characterizes Moreland’s confinement as a mere curfew, it can do so only by ignoring the record. For example, the court suggests that More-land was subject only to a midnight to 8:00 a.m. curfew during his confinement at the *665Center and that Moreland was subject to fewer restrictions than those imposed on the defendant in Brown v. Rison, 895 F.2d 533 (9th Cir.1990) (prisoner in custody of halfway house for 10 hours every day subject to official custody). See ante at 662 n. 6. Both of these assertions are incorrect.
The record reveals that Moreland was completely confined twenty-four hours a day in the Center during his first two weeks of custody there. Not only was Moreland barred from leaving the grounds during that time, but he was subject to the liberty restrictions, rules, and regulations of the Center. These rules included: no drugs, narcotics, or alcohol; no weapons, sharp instruments, or knives; random urine and breath tests; nightly bed checks; no smoking in room; limited visiting hours, with all visiting to take place in the Center’s dining room; and telephone use limited to ten minutes. These restrictions mirror those imposed on jail inmates.2 The Bureau of Prisons’ policy statement, however, makes no allowance for a situation such as Moreland’s. I cannot see how the total confinement Moreland was subjected to for two weeks can be considered less restrictive than incarceration and undeserving of sentence credit, and the court does not offer a reason for its conclusion to the contrary.
After two weeks of total confinement, the Center gradually increased the amount of time that Moreland could be away from the Center. During this time, Moreland’s conditions of confinement were more restrictive or equally restrictive as the 10 hours of daily confinement held to be custody in Brown v. Rison. Brown, 895 F.2d at 536. For two weeks, Moreland was allowed to seek employment at the Center’s direction between 8:00 a.m. and 4:00 p.m. (sixteen hours of confinement a day). Moreland then was granted a 7:00 p.m. curfew for the two weeks after he found a job (thirteen hours of confinement a day). The Center then imposed a 10:00 p.m. curfew upon Moreland (ten hours of confinement a day). It was not until Moreland had been at the Center for approximately two months that he was subject to a midnight to 8:00 a.m. curfew.3 At all times, the Center subjected Moreland to a compulsory sign-in and sign-out surveillance system. The Center required Moreland to provide an accurate address and telephone number of his destination when signing out, monitored his whereabouts at all times while outside the center, and subjected him to telephone checks during that time.
In short, the Center subjected Moreland to 24-hour supervision and physically incarcerated him for a substantial part of each day for 150 days. Indeed, for part of his confinement at the Center, Moreland was subject to significantly stricter liberty restrictions than those in Brown v. Rison. Moreover, as I noted earlier, the Center acted at the behest of the criminal justice system. Moreland was subject to “official detention,” and to deny him sentence credit is unreasonable and contrary to the considerations of fairness that inspired Congress’ decision to provide credit for time served. Brown, 895 F.2d at 536.
Moreland’s Conditional Release
The court places great weight on the fact that the Magistrate-Judge granted More-land a conditional release within the meaning of 18 U.S.C. 31424 when he released Moreland on bond and ordered him to be held in custody at the Center and to obey *666its rules. This emphasis is misplaced and focusses attention away from the true issue in this case. The question is not whether Moreland was “detained” within the meaning of the Bail Reform Act, but whether the time he served in custody at the Center was “official detention” under 18 U.S.C. § 3585(b)(1). The degree of restraint provided by residence in a community center is the operative question here; terms used in the Bail Reform Act do not apply to the statute at issue here, and the court’s discussion of the Bail Reform Act is a non sequitur.5
Equal Protection
It is undisputed that Moreland was subject to the same conditions of confinement as prisoners who were completing their sentence at the Center. All inmates at the Center are under the same rules and conditions whether they are presentence or post-sentence detainees. Moreland, however, will not receive sentence credit, but post-sentence detainees who lived under identical conditions will. In my view, this disparate treatment of similarly situated groups without a rational basis for the disparity violates the Constitution. See Johnson v. Smith, 696 F.2d 1334 (11th Cir.1983).
The court justifies this result by focusing on the “legal custody status” of presen-tence and postsentence inmates. According to the court, presentence detainees released to a halfway house are placed in the least restrictive conditions possible, while postsentence detainees are in the custody of the Attorney General, with the Bureau of Prisons assigning inmates to various institutions based on security and other factors. This focus is misleading.
First, the legal status of presentence and postsentence detainees is not as different as the court suggests. If Moreland had escaped from the Center he would have been subject to criminal penalties similar to those applicable if he had been a postsen-tence detainee. Compare U.S.S.G. 2J1.6 (failure to appear by defendant) with U.S.S.G. § 2P1.1 (escape). In fact, some courts have gone one step further, holding that the escape statute applies to a pretrial detainee such as Moreland. See United States v. Rindgo, 411 A.2d 373 (D.C.1980) (defendant in pretrial detention at halfway house subject to escape charges under 18 U.S.C. 751); United States v. Vaughn, 446 F.2d 1317 (D.C.Cir.1971) (pretrial detainee who participated in work-release program under authority of Bail Reform Act and escaped held subject to escape charges under 18 U.S.C. 751).6
Moreover, I do not see how a delineation of the paths by which people become residents or a recitation of official goals and reasons leading to their residential status can adequately serve as a rational basis for differing treatment. Nobody would contend that the Bureau of Prisons could justify a denial of sentence credit to presen-tence detainees in county jails because their legal status differed from postsen-tence defendants. Under the statute, the degree of confinement is what is at issue, *667and the restraints on Moreland’s liberty at the Center were the same as those who were concluding a sentence there. Moreover, as the court acknowledges, the restrictions on Moreland’s liberty were among the most severe that could have been imposed as a condition of pretrial release. The government placed Moreland into a halfway house not only to ensure his appearance at trial but also to protect the community, a goal that is perhaps the central purpose of incarceration today.
For the foregoing reasons I dissent.
. We previously have suggested that custody or detention may not require incarceration in a jail. In Carruthers v. United States, 525 F.2d 843, 844 (8th Cir.1975), we dismissed a claim for sentence credit for time spent on parole because the petitioner’s claim was too "sparse and conclusory” to demonstrate that the degree of restraint imposed on him at the halfway house entitled him to sentence credit. The dismissal was without prejudice, and permitted the petitioner to refile if he could show that his time in the halfway house "was, in effect, a form of custody or confinement." Id.
. Significantly, Moreland was not confined to the relative comfort of his home during his time at the Center. Compare United States v. Wickman, 955 F.2d 592 (8th Cir.1992) (en banc) (per curiam) (Lay & McMillian, JJ., dissenting) (defendant not entitled to sentence credit for days spent under pre-trial house arrest).
. The court’s opinion suggests that Moreland had limited phone privileges during his midnight to 8:00 a.m. curfew. The record indicates otherwise. According to the Center’s rules, Moreland was subject to "periodic bed checks ... throughout the night,” so the Center must have required residents to be in their rooms during the nightly curfew. It does not appear that residents had personal phones in their rooms, as the Rules refer only to use of "the residence telephone” (emphasis added).
. The Bail Reform Act of 1984 and its amendments.
. If the language of the Bail Reform Act were relevant to Congress’ intent concerning sentence credit, then that Act's repeated references to "custody” in the context of conditional release would support the conclusion that defendants confined to restrictive "custody” are eligible for sentence credit. The Bail Reform Act permits a judicial officer to "release" a defendant under conditions that require the defendant to be placed in the custody of a designated person, be physically constrained in that person’s custody for specified hours, and satisfy other conditions deemed necessary by a judicial officer. See 18 U.S.C. §§ 3142(c)(1)(B)(i)-3142(c)(B)(1)(xiv) (1988). If the statutory terms "official detention" and "in custody” are interchangeable for sentence credit purposes, as the court claims, see ante at 662 n. 6, and if terms used in the Bail Reform Act apply to sentence credit issues, then defendants granted conditional release but placed in "custody” under the Bail Reform Act should be granted sentence credit under section 3585. Moreover, the present statute is entitled "Credit for prior custody," see 18 U.S.C. § 3585(b) (emphasis added).
. Other courts, perhaps more wisely, have declined to hold that pretrial detainees are subject to prosecution for escape under section 751. See Randall v. Whelan, 938 F.2d 522, 525 (4th Cir.1991) (pretrial detainees released on bond not immediately subject to prosecution for escape under section 751); United States v. Miranda, 749 F.Supp. 1062 (D.Colo.1990) (pretrial defendant released on conditions of bond not subject to prosecution for escape under section 751).