Income Taxes - Schedule of Income Tax Exepnse (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal	$ 18,458	$ 16,451	$ 29,866
State	2,818	2,759	4,481
Total current	21,276	19,210	34,347
Deferred:
Federal	7,697	2,131	(15,268)
State	1,065	274	(1,989)
Total deferred	8,762	2,405	(17,257)
Total income tax expense	$ 30,038	$ 21,615	$ 17,090