Summary of Provision for Income Taxes from Continuing Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current income taxes (benefit)
Federal	$ 0	$ 1,279	$ (109,240)
State	(26)	(3,933)	876
Current Income Tax Expense (Benefit), Total	(26)	(2,654)	(108,364)
Deferred income taxes (benefit)
Federal	(60,676)	(80,529)	67,999
State	(8,000)	(4,972)	(2,486)
Deferred Income Tax Expense (Benefit), Total	(68,676)	(85,501)	65,513
Income tax benefit	$ (68,702)	$ (88,155)	$ (42,851)