Income Taxes - Components of Income Tax Expense (Benefit) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current:
Federal									$ 40,949	$ 36,367	$ 7,323
State									5,540	7,462	2,715
Current Income Tax Expense (Benefit), Total									46,489	43,829	10,038
Deferred:
Federal									4,209	(448)	18,125
State									898	32	2,679
Deferred Income Tax Expense (Benefit)									5,107	(416)	20,804
Tax expense recorded as an increase of paid-in capital									4,588	564	140
Income Tax Expense (Benefit), Total	$ 14,215	$ 15,714	$ 12,048	$ 14,207	$ 12,097	$ 12,594	$ 9,748	$ 9,538	$ 56,184	$ 43,977	$ 30,982