INCOME TAXES (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current income tax expense (benefit):
Federal									$ (86,157)	$ 9,942	$ (109,092)
State									34,760	69,026	2,916
Foreign											1,758
Total current income tax expense (benefit)									(51,397)	78,968	(104,418)
Deferred income tax expense (benefit):
Federal									193,834	55,083	127,668
State									(7,706)	(48,273)	11,571
Foreign									3,369	5,567	(12,107)
Total deferred income tax expense (benefit)									189,497	12,377	127,132
Provision (benefit) for income taxes	$ 37,133	$ 35,253	$ 35,205	$ 30,509	$ 29,357	$ 26,576	$ 22,386	$ 13,026	$ 138,100	$ 91,345	$ 22,714
Difference between the effective tax rate implicit in the consolidated financial statements and the statutory federal income tax rate
Federal income tax provision at statutory rate (as a percent)									35.00%	35.00%	35.00%
State franchise taxes, net of federal tax effect (as a percent)									4.30%	5.30%	8.10%
Tax credits (as a percent)									(2.70%)	(4.80%)	(6.90%)
Foreign subsidiaries acquisition (as a percent)											(14.40%)
Other, net (as a percent)									(0.60%)	0.20%	(0.10%)
Effective income tax rate (as a percent)									36.00%	35.70%	21.70%