Fair Value Measurements - Qualitative Valuation (Details)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	$ 0	$ 8,081,000
Real estate owned	0	92,000
Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	1,063,000	125,000
Real estate owned		92,000
Mortgage servicing rights	681,000	442,000
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	6,219,008,000	4,841,830,000
Significant Unobservable Inputs (Level 3) | Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	1,063,000	125,000
Real estate owned		92,000
Mortgage servicing rights	$ 681,000	$ 442,000
Significant Unobservable Inputs (Level 3) | Measurement Input, Expected Value Of Future Cash Flows | Measured on non-recurring basis | Impaired loans | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0
Significant Unobservable Inputs (Level 3) | Measurement Input, Expected Value Of Future Cash Flows | Measured on non-recurring basis | Impaired loans | Weighted Average | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0
Significant Unobservable Inputs (Level 3) | Measurement Input, Prepayment Rate and Discount Rate | Measured on non-recurring basis | Mortgage servicing rights | Weighted Average | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0.127
Significant Unobservable Inputs (Level 3) | Measurement Input, Discount Rate | Measured on non-recurring basis | Impaired loans | Appraisal
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) | Measurement Input, Discount Rate | Measured on non-recurring basis | Impaired loans | Weighted Average | Appraisal
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) | Measurement Input, Discount Rate | Measured on non-recurring basis | Real estate owned | Contract Sales Price
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) | Measurement Input, Discount Rate | Measured on non-recurring basis | Real estate owned | Weighted Average | Contract Sales Price
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) | Measurement Input, Prepayment Rate | Measured on non-recurring basis | Mortgage servicing rights | Weighted Average | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.120
Significant Unobservable Inputs (Level 3) | Measurement Input, Prepayment Rate | Measured on non-recurring basis | Mortgage servicing rights | Minimum | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0.036	0.033
Significant Unobservable Inputs (Level 3) | Measurement Input, Prepayment Rate | Measured on non-recurring basis | Mortgage servicing rights | Maximum | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0.240	0.268
Significant Unobservable Inputs (Level 3) | Measurement Input, Prepayment Rate | Measured on non-recurring basis | SBA servicing rights | Weighted Average | Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.1175