Fair Value Qualitative information about Level 3 fair value measurements (Details) $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value	$ 2,154	$ 2,090
Other Assets, Fair Value Disclosure	6,451,435	6,426,869
Loans Held-for-sale, Fair Value Disclosure	23,901	12,278
Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value	2,154	2,090
Other Assets, Fair Value Disclosure	6,451,435	6,426,869
Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Assets, Fair Value Disclosure	2,977	3,033
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Assets, Fair Value Disclosure	2,977	3,033
Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value		1,873
Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Assets, Fair Value Disclosure	2,295	2,295
Fair Value, Nonrecurring [Member] | Residential Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Assets, Fair Value Disclosure	682	738
Fair Value, Nonrecurring [Member] | Residential Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Assets, Fair Value Disclosure	682	738
Fair Value, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value		217
Fair Value, Nonrecurring [Member] | Residential Real Estate [Member] | Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Assets, Fair Value Disclosure	682	738
Estimate of Fair Value Measurement [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value		$ 2,090
Estimate of Fair Value Measurement [Member] | Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value	1,990
Estimate of Fair Value Measurement [Member] | Fair Value, Nonrecurring [Member] | Residential Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loan Fair Value	$ 164
Measurement Input, Comparability Adjustment [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0	0
Measurement Input, Comparability Adjustment [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	1.390	0.560
Measurement Input, Comparability Adjustment [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0.214	0.265
Measurement Input, Comparability Adjustment [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.009	0.009
Measurement Input, Comparability Adjustment [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.684	0.684
Measurement Input, Comparability Adjustment [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.347	0.347
Measurement Input, Comparability Adjustment [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0	0
Measurement Input, Comparability Adjustment [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0.535	0.535
Measurement Input, Comparability Adjustment [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0.142	0.108
Measurement Input, Comparability Adjustment [Member] | Residential Real Estate [Member] | Real Estate [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.046	0.046
Measurement Input, Comparability Adjustment [Member] | Residential Real Estate [Member] | Real Estate [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.546	0.546
Measurement Input, Comparability Adjustment [Member] | Residential Real Estate [Member] | Real Estate [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.394	0.392
Measurement Input, Cap Rate [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Minimum [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0.200
Measurement Input, Cap Rate [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Maximum [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0.200
Measurement Input, Cap Rate [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Weighted Average [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input	0.200
Measurement Input, Cap Rate [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Minimum [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.130	0.130
Measurement Input, Cap Rate [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Maximum [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.130	0.130
Measurement Input, Cap Rate [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Weighted Average [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate Owned, Measurement Input	0.130	0.130
Measurement input replacement cost [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Minimum [Member] | Valuation, Cost Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input		0.931
Measurement input replacement cost [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Maximum [Member] | Valuation, Cost Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input		0.931
Measurement input replacement cost [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Weighted Average [Member] | Valuation, Cost Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired Loans Receivable, Measurement Input		0.931