Mortgage Servicing Rights - Sensitivity Analysis (Details) - MSR - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Sensitivity analysis
Constant prepayment rate: Impact of 10% adverse change	$ (5,639)	$ (3,072)
Constant prepayment rate: Impact of 20% adverse change	(11,164)	(5,943)
Discount rate: Impact of 10% adverse change	(6,435)	(2,094)
Discount rate: Impact of 20% adverse change	(12,287)	(4,028)
Contractually specified servicing fees, late fees and ancillary fees	$ 35,400	$ 25,300	$ 23,300