Significant Accounting Policies (Accumulated Other Comprehensive Income) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 26,984,000	$ 16,600,000	$ 500,000
Other comprehensive income (loss) before reclassifications	(45,900,000)	31,700,000	37,300,000
Amounts reclassified from accumulated other comprehensive income	(14,000,000)	(21,300,000)	(21,200,000)
Other comprehensive (loss) income, net of tax	(59,851,000)	10,352,000	16,145,000
Ending balance	(32,867,000)	26,984,000	16,600,000
Unrealized Gains (Losses) on investments available-for-sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	38,000,000	29,800,000	5,300,000
Other comprehensive income (loss) before reclassifications	(50,700,000)	32,100,000	46,000,000
Amounts reclassified from accumulated other comprehensive income	(15,600,000)	(23,900,000)	(21,500,000)
Other comprehensive (loss) income, net of tax	(66,300,000)	8,200,000	24,500,000
Ending balance	(28,300,000)	38,000,000	29,800,000
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(11,000,000)	(13,200,000)	(4,800,000)
Other comprehensive income (loss) before reclassifications	4,800,000	(400,000)	(8,700,000)
Amounts reclassified from accumulated other comprehensive income	1,600,000	2,600,000	300,000
Other comprehensive (loss) income, net of tax	6,400,000	2,200,000	(8,400,000)
Ending balance	$ (4,600,000)	$ (11,000,000)	$ (13,200,000)