Significant Accounting Policies (Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (14,500,000)	$ 10,300,000	$ (32,867,000)	$ 27,000,000
Other comprehensive income (loss) before reclassifications	15,200,000	(42,600,000)	33,700,000	(48,500,000)
Amounts reclassified from accumulated other comprehensive (loss) income	(1,200,000)	(3,300,000)	(1,300,000)	(14,100,000)
Other comprehensive income (loss), net of tax	14,059,000	(45,885,000)	32,416,000	(62,593,000)
Ending balance	(451,000)	(35,600,000)	(451,000)	(35,600,000)
Unrealized Gains (Losses) on investments available-for-sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(10,000,000)	20,900,000	(28,300,000)	38,000,000
Other comprehensive income (loss) before reclassifications	15,200,000	(42,600,000)	33,700,000	(48,500,000)
Amounts reclassified from accumulated other comprehensive (loss) income	(1,300,000)	(3,700,000)	(1,500,000)	(14,900,000)
Other comprehensive income (loss), net of tax	13,900,000	(46,300,000)	32,200,000	(63,400,000)
Ending balance	3,900,000	(25,400,000)	3,900,000	(25,400,000)
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,500,000)	(10,600,000)	(4,600,000)	(11,000,000)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	100,000	400,000	200,000	800,000
Other comprehensive income (loss), net of tax	100,000	400,000	200,000	800,000
Ending balance	$ (4,400,000)	$ (10,200,000)	$ (4,400,000)	$ (10,200,000)