Investment Securities - Gains and (Losses) Recognized in Earnings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Securities in unrealized loss positions, qualitative disclosure, number of positions (in security) | security	1,351		1,351
Proceeds	$ 10,050	$ 4,356	$ 10,050	$ 5,000
Gross gains	$ 77	$ 18	$ 167	$ 37