Investment Securities - Debt Securities Credit Loss Recognized in Income, and Other Losses Recorded in Other Comprehensive Income (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Credit losses on debt securities held:
Beginning balance	$ 500	$ 11,355
Reductions for previous other-than-temporary losses realized on securities sold during the year	(500)	(10,855)
Ending balance	$ 0	$ 500