Income Taxes Income Taxes (Income Tax Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Income before income taxes	$ 53,717	$ 123,157	$ 85,570
Federal income tax expense at statutory rate	18,801	43,105	29,950
Increases (decreases) resulting from:
State income taxes, net of federal income tax benefits	3,009	6,444	1,121
Non-deductible expenses	3,311	1,974	1,491
Impact of domestic production deduction	(2,026)	(4,256)	(654)
Tax credits	0	0	(25)
Changes in valuation allowance, net of equity and tax audit adjustments	0	870	(397)
Income tax expense	$ 23,095	$ 48,137	$ 31,486