Mortgage Banking - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) CPR	Dec. 31, 2015 USD ($) CPR	Dec. 31, 2014 USD ($)
Schedule of changes in the reserve for mortgage loan [Abstract]
Assumed average prepayment speed | CPR	7.94	9.32
Average discount rate (in hundredths)	10.32%	10.35%
Annual servicing fee	$ 20,400	$ 19,300	$ 18,600
Servicing fee income percentage of outstanding balance of underlying loans (in hundredths)	0.33%
Mortgage servicing rights [Abstract]
Residential mortgage loans sold	$ 1,384,000	1,246,000	913,500
Gains on sales of residential mortgage loans, before tax	$ 20,500	18,000	10,800
Period of putback response	60 days
Mortgage loan servicing putback expenses	$ 420	$ 315	$ 600