Derivative Instruments and Balance Sheet Offsetting - Net Gains (Losses) Related to Changes in Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative instruments
Total gain (loss) recognized in income	$ 229	$ 227	$ 738	$ 242
Forward contracts related to mortgage loans to be delivered for sale | Net gain (loss) on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	(21)	959	(391)	(18)
Interest rate lock commitments | Net gain (loss) on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	211	(181)	763	1,041
Customer-initiated derivatives | Other noninterest income
Derivative instruments
Total gain (loss) recognized in income	$ 39	$ (551)	$ 366	$ (781)