Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Fair Value Assets Transfers between Level 1 and Level 2) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount	$ 0	$ 23,586	$ 0	$ 40,435
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount	0	11,068	14,012	22,224
Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount	0	13,940	0	30,789
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount	0	0	14,012	11,156
Corporate securities | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount	0	11,777	0	14,773
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount	0	0	14,012	4
US Treasury And Government Member | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount			0	0
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount			0	11,152
State and political subdivisions | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount			0	12,794
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount			0	0
Other foreign government, supranational and foreign government-sponsored enterprises | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount	0	2,163	0	3,222
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount	0	0	0	0
Nonredeemable Preferred Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets, Level 1 to level 2 Transfers During Period, Amount	0	9,646	0	9,646
Fair Value Assets, Level 2 to Level 1 Transfers During Period, Amount	$ 0	$ 11,068	$ 0	$ 11,068