Servicing Rights - Key Assumptions and the Sensitivity of the Fair Value (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Servicing Assets at Fair Value [Line Items]
Aggregate portfolio principal balance	$ 750,327	$ 683,117
Base
Percentage of MSR (percent)	1.74%	1.64%
Mortgage servicing rights
Servicing Assets at Fair Value [Line Items]
Aggregate portfolio principal balance	$ 750,327	$ 683,117
Weighted average rate of note (percent)	3.36%	3.62%
Base
Constant prepayment rate (percent)	12.31%	13.05%
Discount rate (percent)	8.00%	7.75%
Fair value MSR	$ 13,080	$ 11,218	$ 12,835	$ 10,589	$ 10,721	$ 11,920
Percentage of MSR (percent)	1.74%	1.64%
1.0% Adverse Rate Change
Constant prepayment rate (percent)	24.63%	26.11%
Discount rate (percent)	7.00%	6.75%
Fair value MSR	$ 9,134	$ 7,455
Percentage of MSR (percent)	1.22%	1.09%
2.0% Adverse Rate Change
Constant prepayment rate (percent)	36.19%	38.97%
Discount rate (percent)	6.00%	5.75%
Fair value MSR	$ 6,894	$ 5,404
Percentage of MSR (percent)	0.92%	0.79%