Investment Securities Summary of Cumulative Other-than-Temporary Impairment Charges Recognized as Components of Earnings (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance of cumulative credit losses on debt securities, beginning of period	$ (23,079)	$ (22,692)	$ (23,079)	$ (22,781)
Reductions for securities sold during the period	2,468	0	2,468	0
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	4	0	4	89
Balance of cumulative credit losses on debt securities, end of period	$ (20,607)	$ (22,692)	$ (20,607)	$ (22,692)