Investment Securities Available-for-sale gross gains and losses realized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gross gains and gross losses realized from sales of available-for-sale securities:
Gross gains realized	$ 2,999	$ 933	$ 795
Gross losses realized	16	3	66
Net gain realized	$ 2,983	$ 930	$ 729