Mortgage Banking - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) CPR	Dec. 31, 2019 USD ($) CPR	Dec. 31, 2018 USD ($)
Schedule of changes in the reserve for mortgage loan [Abstract]
Assumed average prepayment speed | CPR	15	11
Average discount rate (in hundredths)	9.53%	10.03%
Annual servicing fee	$ 23,300	$ 22,600	$ 21,900
Servicing fee income percentage of outstanding balance of underlying loans (in hundredths)	0.31%
Mortgage servicing rights [Abstract]
Residential mortgage loans sold	$ 2,532,000	1,404,000	1,092,000
Gains on sales of residential mortgage loans	$ 110,900	30,300	$ 21,800
Period of putback response	60 days
Reserve for mortgage loan servicing putback expenses	$ 500	$ 500