Significant Accounting Policies (Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (35,600,000)	$ 7,700,000	$ 26,984,000	$ 16,600,000
Other comprehensive income before reclassifications	700,000	22,400,000	(47,800,000)	28,700,000
Amounts reclassified from accumulated other comprehensive income	200,000	(2,200,000)	(13,900,000)	(17,400,000)
Other comprehensive income (loss), net of tax	914,000	20,255,000	(61,679,000)	11,299,000
Ending balance	(34,695,000)	27,900,000	(34,695,000)	27,900,000
Unrealized Gains (Losses) on investments available-for-sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(25,400,000)	19,600,000	38,000,000	29,800,000
Other comprehensive income before reclassifications	700,000	22,400,000	(47,800,000)	28,700,000
Amounts reclassified from accumulated other comprehensive income	(200,000)	(2,800,000)	(15,100,000)	(19,300,000)
Other comprehensive income (loss), net of tax	500,000	19,600,000	(62,900,000)	9,400,000
Ending balance	(24,900,000)	39,200,000	(24,900,000)	39,200,000
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(10,200,000)	(11,900,000)	(11,000,000)	(13,200,000)
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	400,000	600,000	1,200,000	1,900,000
Other comprehensive income (loss), net of tax	400,000	600,000	1,200,000	1,900,000
Ending balance	$ (9,800,000)	$ (11,300,000)	$ (9,800,000)	$ (11,300,000)