Assets and Liabilities Measured at Fair Value - Quantitative information about Level 3 fair value measurements for fair value on recurring basis (Details) - Recurring - Level 3	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Servicing rights for SBA/USDA loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Discounted cash flow
Servicing rights for SBA/USDA loans | Discount rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights for SBA/USDA loans, measurement input	0.076	0.123
Servicing rights for SBA/USDA loans | Prepayment rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights for SBA/USDA loans, measurement input	0.182	0.165
Residential mortgage servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Discounted cash flow
Residential mortgage servicing rights | Discount rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Residential mortgage servicing rights, measurement input	0.100	0.100
Residential mortgage servicing rights | Prepayment rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Residential mortgage servicing rights, measurement input	0.187	0.141
Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Indicative bid provided by a broker
Derivative assets - customer derivative positions
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Internal model
Derivative assets - customer derivative positions | Probability of default rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative assets, measurement input	0.537
Derivative assets - customer derivative positions | Loss given default rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative assets, measurement input	1
Derivative assets - mortgage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Internal model
Derivative assets - mortgage | Pull through rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative assets, measurement input	0.832	0.836
Derivative assets and liabilities - other
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Dealer priced
Derivative assets & liabilities - risk participations
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Valuation technique	Internal model
Derivative assets & liabilities - risk participations | Probability of default rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset and liabilities, measurement input	0.0188	0.0180
Derivative assets & liabilities - risk participations | Probable exposure rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset and liabilities, measurement input	0.0105	0.0036