Stockholders' Equity - Reclassification out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Tax Expense (Benefit)	$ 10,372	$ 1,796	$ 7,105	$ 3,493
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			65
Unrealized Gains on Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax			54	40
Income Tax Expense (Benefit)			(20)	(15)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			34	25
Unrecognized Net Actuarial Loss and Prior Service Credit, Net
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax			(345)	(413)
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax			275	353
Income Tax Expense (Benefit)			101	23
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			$ 31	$ (37)