Segment Information (Details 2) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segment information
Revenue	$ 359,849	$ 276,948	$ 708,749	$ 592,563
Derivative gain (loss)	40,590	46,902	(45,089)	39,666
Total revenue	400,439	323,850	663,660	632,229
Portion of operating income attributable to non-controlling interests	16,528	6,764	30,077	11,901
Facility expenses adjustments	2,855	2,851	5,710	3,390
Selling, general and administrative expenses	(18,580)	(16,419)	(40,292)	(37,927)
Depreciation	(37,201)	(29,818)	(71,565)	(58,005)
Amortization of intangible assets	(10,830)	(10,193)	(21,647)	(20,386)
Gain (loss) on disposal of property, plant and equipment	(2,373)	(188)	(4,472)	(179)
Accretion of asset retirement obligations	(290)	(69)	(377)	(212)
Income from operations	133,214	109,071	117,920	162,644
(Loss) earnings from unconsolidated affiliate	(216)	1,585	(755)	1,517
Interest income	63	377	152	763
Interest expense	(27,874)	(25,755)	(56,137)	(49,537)
Amortization of deferred financing costs and discount (a component of interest expense)	(1,443)	(2,280)	(2,871)	(4,892)
Derivative gain related to interest expense				1,871
Loss on redemption of debt			(43,328)
Miscellaneous income (expense), net	169	(9)	131	1,053
Income before provision for income tax	103,913	82,989	15,112	113,419
Total reportable segments
Segment information
Revenue	362,271	276,948	719,114	592,563
Portion of operating income attributable to non-controlling interests	16,528	6,764	30,077	11,901
Income from operations	147,798	102,069	296,224	230,529
Southwest Segment
Segment information
Revenue	235,575	155,043	437,349	320,007
Portion of operating income attributable to non-controlling interests	1,346	1,556	2,518	3,056
Revenue deferral adjustment	200		6,700
Income from operations	84,386	62,703	161,635	131,053
Northeast Segment
Segment information
Revenue	53,676	81,322	145,767	193,170
Revenue deferral adjustment	2,200		3,600
Income from operations	31,045	19,526	76,664	60,062
Unallocated Segment
Segment information
Derivative gain (loss)	40,590	46,902	(45,089)	39,666
Derivative (loss) gain not allocated to segments	37,917	54,360	(64,145)	34,541
Revenue deferral adjustment	2,422		10,365
Compensation expense included in facility expenses not allocated to segments	$ (188)	$ (286)	$ (1,228)	$ (1,008)