Mortgage Servicing Rights - Schedule of Servicing Income and Expense Included in Mortgage Banking Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Servicing income:
Servicing income	$ 5,604	$ 2,747	$ 10,397	$ 5,495
Change in fair value of mortgage servicing rights	(15)	(1,840)	3,528	(2,341)
Change in fair value of mortgage servicing rights hedging instruments	(1,763)		(7,019)
Gross servicing income	3,826	907	6,906	3,154
Servicing expense:
Loss on sale of mortgage servicing rights		249		249
Direct servicing expenses	2,078	1,204	3,873	2,138
Gross servicing expense	2,078	1,453	3,873	2,387
Net servicing income	$ 1,748	$ (546)	$ 3,033	$ 767