Significant Accounting Policies (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 7,300	$ (14,500)	$ (3,261)	$ (32,900)
Other comprehensive income (loss) before reclassifications	(20,200)	15,200	(9,600)	33,700
Amounts reclassified from accumulated other comprehensive (loss) income	(600)	(1,200)	(600)	(1,300)
Other comprehensive (loss) income, net of tax	(20,837)	14,059	(10,278)	32,416
Ending balance	(13,539)	(500)	(13,539)	(500)
Unrealized Gains (Losses) on investments available-for-sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	18,400	(10,000)	8,200	(28,300)
Other comprehensive income (loss) before reclassifications	(20,200)	15,200	(9,600)	33,700
Amounts reclassified from accumulated other comprehensive (loss) income	(1,000)	(1,300)	(1,400)	(1,500)
Other comprehensive (loss) income, net of tax	(21,200)	13,900	(11,000)	32,200
Ending balance	(2,800)	3,900	(2,800)	3,900
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(11,100)	(4,500)	(11,500)	(4,600)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	400	100	800	200
Other comprehensive (loss) income, net of tax	400	100	800	200
Ending balance	$ (10,700)	$ (4,400)	$ (10,700)	$ (4,400)