Income Taxes - Provision for Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal	$ 76,599	$ 45,112	$ 96,449
State	3,066	8,004	12,468
Deferred:
Federal	13,086	21,492	6,352
State	1,738	3,548	1,119
Total	$ 94,489	$ 78,156	$ 116,388