Fair Value Qualitative information about Level 3 fair value measurements (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	$ 5,287,881	$ 5,178,439
Impaired Loan Fair Value	7,137	5,983
Other Assets, Fair Value Disclosure	5,269,250	5,161,919
Loans Held-for-sale, Fair Value Disclosure	11,396	10,413
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	5,276,387	5,167,902
Impaired Loan Fair Value	7,137	5,983
Other Assets, Fair Value Disclosure	5,269,250	5,161,919
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	7,137	5,983
Other Assets, Fair Value Disclosure	6,762	6,897
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	7,137	5,983
Other Assets, Fair Value Disclosure	6,762	6,897
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	3,212	3,322
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	$ 3,212	3,322
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Loans Receivable [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	0.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Loans Receivable [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	4.80%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Loans Receivable [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	2.40%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	$ 3,212	$ 3,322
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	0.00%	0.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member] | Minimum [Member] | Bulk Sale Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	15.00%	15.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	90.00%	90.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member] | Maximum [Member] | Bulk Sale Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	15.00%	15.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	24.40%	24.70%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Real Estate [Member] | Weighted Average [Member] | Bulk Sale Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	15.00%	15.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	$ 6,147	$ 3,057
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]
Loans Receivable, Fair Value Disclosure	$ 6,147	3,057
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired Loan Fair Value		$ 3,057
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	0.00%	0.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	8.80%	9.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Minimum [Member] | Cost Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Accumulated Depreciation	90.10%	17.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	102.00%	90.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	12.50%	10.60%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Maximum [Member] | Cost Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Accumulated Depreciation	90.10%	18.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	40.10%	20.20%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	9.40%	10.10%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans Receivable [Member] | Weighted Average [Member] | Cost Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Accumulated Depreciation	90.10%	17.80%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	$ 2,457	$ 2,644
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	0.00%	0.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	12.00%	13.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	68.40%	68.40%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	13.00%	14.00%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	28.90%	26.50%
Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	12.90%	13.10%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired Loan Fair Value		$ 541
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments		0.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member] | Minimum [Member] | Bulk Sale Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate		10.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments		11.10%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member] | Maximum [Member] | Bulk Sale Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate		10.00%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments		1.60%
Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate - Remaining Commercial [Member] | Loans Receivable [Member] | Weighted Average [Member] | Bulk Sale Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate		10.00%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	$ 1,093	$ 931
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	$ 1,093	931
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired Loan Fair Value		$ 2,385
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	0.10%	0.30%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	10.50%	10.00%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	33.00%	110.00%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	10.50%	10.00%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	11.70%	17.00%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Loans Receivable [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Cap Rate	10.50%	10.00%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Assets, Fair Value Disclosure	$ 1,093	$ 931
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Real Estate [Member] | Minimum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	1.20%	3.20%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Real Estate [Member] | Maximum [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	79.70%	79.70%
Fair Value, Measurements, Nonrecurring [Member] | Residential Real Estate [Member] | Real Estate [Member] | Weighted Average [Member] | Sales Comparison Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Comparability Adjustments	30.80%	30.60%
Construction Real Estate - Remaining Commercial [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	$ 127	$ 541
Construction Real Estate - Remaining Commercial [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	127	541
Fair Value [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired Loan Fair Value		$ 5,983
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]
Loans Receivable, Fair Value Disclosure	6,147
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]
Loans Receivable, Fair Value Disclosure	863
Fair Value [Member] | Construction Real Estate - Remaining Commercial [Member] | Fair Value, Measurements, Nonrecurring [Member] | Construction Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans Receivable, Fair Value Disclosure	$ 127