Investment Securities - Realized Gains and Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 273	$ 193	$ 1,518
Gross realized losses	136	187	203
Net realized gains	$ 137	$ 6	$ 1,315