Investment Securities - Credit loss rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 747	$ 800
Amounts related to credit loss for which an OTTI charge was not previously recognized	0	0
Change in value attributable to other factors	0	(53)
Ending balance	$ 747	$ 747