Fair Value Measurements - Valuation Assumptions (Details)	Sep. 30, 2020	Dec. 31, 2019
Discount rate | In-house valuation of collateral, External pricing model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan measured for impairment, measurement input (percent)	0.40	0.25
Discount rate | Discounted cash flow | Mortgage servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)	0.0775
Discount rate | Discounted cash flow | Mortgage servicing rights | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)		0.0851
Discount rate | Discounted cash flow | Mortgage servicing rights | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)		0.0866
Discount rate | Discounted cash flow | Commercial servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)	0.1170	0.1170
Pull through rate | In-house valuation of collateral, External pricing model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock commitment, measurement input (percent)	0.9024	0.9265
Constant prepayment rate | Discounted cash flow | Mortgage servicing rights | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)	0.0954	0.0911
Constant prepayment rate | Discounted cash flow | Mortgage servicing rights | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)	0.1450	0.1067
Constant prepayment rate | Discounted cash flow | Commercial servicing rights | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)	0.0764	0.0764
Constant prepayment rate | Discounted cash flow | Commercial servicing rights | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights, measurement input (percent)	0.1567	0.1567