Mortgage Servicing Assets - Schedule of Range and Weighted-Average of Significant Unobservable Inputs (Details) - Discounted cash flow - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commercial Mortgage Backed Securities | Minimum
Servicing Assets at Fair Value [Line Items]
Expected defaults	101.00%	97.00%
Discount rate	742.00%	700.00%
Escrow earn rate	94.00%	120.00%
Loan assumption rate	0.00%	1.00%
Commercial Mortgage Backed Securities | Maximum
Servicing Assets at Fair Value [Line Items]
Expected defaults	2.00%	2.00%
Discount rate	10.59%	11.42%
Escrow earn rate	1.22%	1.92%
Loan assumption rate	1.75%	3.37%
Commercial Mortgage Backed Securities | Weighted Average
Servicing Assets at Fair Value [Line Items]
Expected defaults	1.18%	1.14%
Discount rate	9.20%	9.24%
Escrow earn rate	1.10%	1.67%
Loan assumption rate	1.44%	1.32%
Agency residential mortgage-backed securities | Minimum
Servicing Assets at Fair Value [Line Items]
Discount rate	7.51%	7.50%
Servicing cost	$ 62.00	$ 62.00
Prepayment speed	10.55%	10.50%
Agency residential mortgage-backed securities | Maximum
Servicing Assets at Fair Value [Line Items]
Discount rate	8.63%	8.50%
Servicing cost	$ 4,375	$ 8,375
Prepayment speed	50.81%	55.60%
Agency residential mortgage-backed securities | Weighted Average
Servicing Assets at Fair Value [Line Items]
Discount rate	7.55%	7.52%
Servicing cost	$ 72.48	$ 68.14
Prepayment speed	12.82%	17.16%