Schedule of Total Provision for Income Taxes (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Line Items]
Federal, current	$ 8,600,000	$ 15,600,000	$ 43,700,000
State and local, current	1,200,000	3,700,000	9,600,000
Current income tax expense	9,800,000	19,300,000	53,300,000
Federal, deferred	(25,700,000)	(103,100,000)	24,200,000
State and local, deferred	(5,500,000)	(19,300,000)	1,700,000
Deferred income tax expense/(benefit)	(31,161,000)	(122,402,000)	25,927,000
Income tax expense/(benefit)	$ (21,397,000)	$ (103,076,000)	$ 79,195,000