Significant Accounting Policies (Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (3,261,000)	$ (32,900,000)
Other comprehensive income (loss) before reclassifications	10,600,000	18,500,000
Amounts reclassified from accumulated other comprehensive (loss) income	0	(100,000)
Other comprehensive income, net of tax	10,559,000	18,357,000
Ending balance	7,298,000	(14,500,000)
Unrealized Gains (Losses) on investments available-for-sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	8,200,000	(28,300,000)
Other comprehensive income (loss) before reclassifications	10,600,000	18,500,000
Amounts reclassified from accumulated other comprehensive (loss) income	(400,000)	(200,000)
Other comprehensive income, net of tax	10,200,000	18,300,000
Ending balance	18,400,000	(10,000,000)
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(11,500,000)	(4,600,000)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	400,000	100,000
Other comprehensive income, net of tax	400,000	100,000
Ending balance	$ (11,100,000)	$ (4,500,000)