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
	Mar. 31, 2015	Mar. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance of cumulative credit losses on debt securities, beginning of period	$ (16,242)	$ (20,691)
Reductions for securities sold during the period	3,938	0
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	2	4
Balance of cumulative credit losses on debt securities, end of period	$ (12,302)	$ (20,687)