Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment information
Revenue	$ 376,137	$ 399,181
Purchased product costs	152,557	154,555
Facility expenses	59,755	48,840
Income from operations	64,350	51,439
Capital expenditures	631,558	254,263
Total reportable segments
Segment information
Revenue	377,902	401,449
Purchased product costs	152,557	154,555
Net operating margin	225,345	246,894
Facility expenses	62,245	51,255
Portion of operating income (loss) attributable to non-controlling interests	48	1,446
Income from operations	163,052	194,193
Capital expenditures	628,613	252,574
Southwest Segment
Segment information
Revenue	211,446	238,954
Purchased product costs	114,102	104,233
Net operating margin	97,344	134,721
Facility expenses	29,123	32,630
Portion of operating income (loss) attributable to non-controlling interests	1,387	1,446
Income from operations	66,834	100,645
Capital expenditures	26,687	50,583
Northeast Segment
Segment information
Revenue	57,336	86,918
Purchased product costs	19,662	25,687
Net operating margin	37,674	61,231
Facility expenses	6,524	6,378
Income from operations	31,150	54,853
Capital expenditures	1,779	23,302
Liberty Segment
Segment information
Revenue	108,497	75,577
Purchased product costs	18,793	24,635
Net operating margin	89,704	50,942
Facility expenses	22,636	12,247
Income from operations	67,068	38,695
Capital expenditures	319,827	178,689
Utica Segment
Segment information
Revenue	623
Net operating margin	623
Facility expenses	3,962
Portion of operating income (loss) attributable to non-controlling interests	(1,339)
Income from operations	(2,000)
Capital expenditures	280,320
Unallocated Segment
Segment information
Capital expenditures	$ 2,945	$ 1,689