Derivative Instruments and Balance Sheet Offsetting - Net Gains (Losses) Related to Changes in Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative instruments
Total gain (loss) recognized in income	$ (189)	$ (395)	$ 53	$ (551)
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	43	(156)	25	(798)
Foreign exchange forwards | Other noninterest income
Derivative instruments
Total gain (loss) recognized in income	5	0	5	0
Interest rate lock commitments | Net gain (loss) on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	(198)	(179)	843	307
Customer-initiated derivatives | Other noninterest income
Derivative instruments
Total gain (loss) recognized in income	$ (39)	$ (60)	$ (820)	$ (60)