Summary of Significant Accounting Policies (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (3,261)	$ (32,900)	$ 27,000
Other comprehensive (loss) income before reclassifications	(2,900)	31,000	(45,900)
Amounts reclassified from accumulated other comprehensive income	1,500	(1,400)	(14,000)
Other comprehensive (loss) income, net of tax	(1,390)	29,606	(59,851)
Ending balance	(4,651)	(3,261)	(32,900)
Unrealized Gains (Losses) on investments available-for-sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	8,200	(28,300)	38,000
Other comprehensive (loss) income before reclassifications	(6,800)	38,300	(50,700)
Amounts reclassified from accumulated other comprehensive income	(100)	(1,800)	(15,600)
Other comprehensive (loss) income, net of tax	(6,900)	36,500	(66,300)
Ending balance	1,300	8,200	(28,300)
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(11,500)	(4,600)	(11,000)
Other comprehensive (loss) income before reclassifications	3,900	(7,300)	4,800
Amounts reclassified from accumulated other comprehensive income	1,600	400	1,600
Other comprehensive (loss) income, net of tax	5,500	(6,900)	6,400
Ending balance	$ (6,000)	$ (11,500)	$ (4,600)