Fair Value Qualitative information about Level 3 fair value measurements (Details) $ in Thousands	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	$ 5,506,681	$ 5,254,837
Impaired Loan Fair Value	6,247	3,574
Other Assets, Fair Value Disclosure	5,493,865	5,247,021
Loans Held-for-sale, Fair Value Disclosure	6,441	4,148
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	5,500,112	5,250,595
Impaired Loan Fair Value	6,247	3,574
Other Assets, Fair Value Disclosure	5,493,865	5,247,021
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	6,247	3,574
Other Assets, Fair Value Disclosure	3,863	6,520
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	6,247	3,574
Other Assets, Fair Value Disclosure	3,863	6,520
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	889	3,204
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	889	3,204
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	889	3,204
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	4,020	2,735
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	4,020	2,735
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loan Fair Value		2,735
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	2,295	2,295
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loan Fair Value		127
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	679	1,021
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	679	1,021
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loan Fair Value		712
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Assets, Fair Value Disclosure	679	1,021
Fair Value [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loan Fair Value		$ 3,574
Fair Value [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	4,020
Fair Value [Member] | Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans Receivable, Fair Value Disclosure	$ 592
Measurement Input, Comparability Adjustment [Member] | Construction Real Estate [Member] | Loans Receivable [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.050	0.000
Measurement Input, Comparability Adjustment [Member] | Construction Real Estate [Member] | Loans Receivable [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.900	0.048
Measurement Input, Comparability Adjustment [Member] | Construction Real Estate [Member] | Loans Receivable [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.261	0.024
Measurement Input, Comparability Adjustment [Member] | Construction Real Estate [Member] | Real Estate [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.000	0.000
Measurement Input, Comparability Adjustment [Member] | Construction Real Estate [Member] | Real Estate [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.450	0.900
Measurement Input, Comparability Adjustment [Member] | Construction Real Estate [Member] | Real Estate [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.219	0.245
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.000	0.000
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.550	0.900
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.254	0.227
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.010	0.003
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.400	0.330
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.185	0.125
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.009	0.012
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.546	0.797
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.407	0.318
Measurement Input, Discount Rate [Member] | Construction Real Estate [Member] | Real Estate [Member] | Minimum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input		0.150
Measurement Input, Discount Rate [Member] | Construction Real Estate [Member] | Real Estate [Member] | Maximum [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input		0.150
Measurement Input, Discount Rate [Member] | Construction Real Estate [Member] | Real Estate [Member] | Weighted Average [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input		0.150
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.106	0.090
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.118	0.110
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.115	0.099
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Real Estate Owned, Measurement Input	0.130	0.130
Measurement Input, Cap Rate [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Minimum [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.105	0.105
Measurement Input, Cap Rate [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Maximum [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.105	0.105
Measurement Input, Cap Rate [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Weighted Average [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.105	0.105
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.037	0.901
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.901	0.901
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 Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired Loans Receivable, Measurement Input	0.129	0.901