Investment Securities - Summary of securities sales activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 168,891	$ 340,540	$ 199,864
Gross gains on sales	2,082	1,247	1,647
Gross losses on sales	(2,738)	(1,205)	(665)
Net (losses) gains on sales of securities	(656)	42	982
Income tax (benefit) expense attributable to sales	$ 132	$ (14)	$ (371)