Income Taxes Expense (Benefit) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current tax expense (benefit):
Federal	$ 32,957us-gaap_CurrentFederalTaxExpenseBenefit	$ 38,573us-gaap_CurrentFederalTaxExpenseBenefit	$ 41,151us-gaap_CurrentFederalTaxExpenseBenefit
State	1,126	687	(557)
Total	34,083us-gaap_CurrentIncomeTaxExpenseBenefit	39,260us-gaap_CurrentIncomeTaxExpenseBenefit	40,594us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal	18,523	15,357	17,007
State	0	(3,532)	0
Total	18,523us-gaap_DeferredIncomeTaxExpenseBenefit	11,825us-gaap_DeferredIncomeTaxExpenseBenefit	17,007us-gaap_DeferredIncomeTaxExpenseBenefit
Income tax expense	$ 52,606us-gaap_IncomeTaxExpenseBenefit	$ 51,085us-gaap_IncomeTaxExpenseBenefit	$ 57,601us-gaap_IncomeTaxExpenseBenefit

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.