Contractural maturities (Details 3) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 420,703	$ 450,548
Available for Sale, Fair Value
Debt Securities, Available-for-sale	426,424	442,752
Held to Maturity, Amortized Cost
Amortized Cost	740,806	611,490
Held to Maturity, Fair Value
Fair Value	753,263	603,640
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesWithinOneYearAmortizedCost	14,962
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesWithinOneYearFairValue	14,992
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesAfterOneThroughFiveYearsAmortizedCost	104,891
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesAfterOneThroughFiveYearsFair Value	105,531
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesAfterFiveThroughTenYearsAmortizedCost	104,614
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesAfterFiveThroughTenYearsFairValue	106,983
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesAfterTenYearsAmortizedCost	937,042
AvailableForSaleandHeldToMaturityDebtSecuritiesMaturitiesAfterTenYearsFairValue	952,181
AvailableForSaleandHeldToMaturityDebtSecuritiesAmortizedCost	1,161,509
Debt Securities, Available-for-sale and Held-to-maturity Fair Value	1,179,687	1,046,392
U.S. government agency securities
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	10,000
Due after one year to five years	10,002
Due after five to ten years	12,471
Due after ten years	0
Debt Securities, Available-for-sale, Amortized Cost	32,473	32,477
Available for Sale, Fair Value
Due in one year or less	10,003
Due in one year or less	10,154
Due after five to ten years	12,958
Due after ten years	0
Debt Securities, Available-for-sale	33,115	32,038
Held to Maturity, Amortized Cost
Due in one year or less	4,962
Due after one year to five years	7,912
Due after five to ten years	0
Due after ten years	0
Amortized Cost	12,874	0
Held to Maturity, Fair Value
Due in one year or less	4,989
Due after one year to five years	8,008
Due after five to ten years	0
Due after ten years	0
Fair Value	12,997
Debt Securities [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	10,000
Due after one year to five years	82,135
Due after five to ten years	67,458
Due after ten years	261,110
Available for Sale, Fair Value
Due in one year or less	10,003
Due in one year or less	82,652
Due after five to ten years	69,342
Due after ten years	264,427
Available-for-sale Securities	426,424
Held to Maturity, Amortized Cost
Due in one year or less	4,962
Due after one year to five years	22,756
Due after five to ten years	37,156
Due after ten years	675,932
Held to Maturity, Fair Value
Due in one year or less	4,989
Due after one year to five years	22,879
Due after five to ten years	37,641
Due after ten years	687,754
Fair Value	753,263
US Treasury Securities [Member]
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	4,032
Due after five to ten years	0
Due after ten years	0
Amortized Cost	4,032	1,004
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	4,053
Due after five to ten years	0
Due after ten years	0
Fair Value	4,053	1,015
Agency mortgage-backed securities
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	0
Due after one year to five years	70,945
Due after five to ten years	54,798
Due after ten years	117,805
Debt Securities, Available-for-sale, Amortized Cost	243,548	222,491
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	71,305
Due after five to ten years	56,181
Due after ten years	119,514
Debt Securities, Available-for-sale	247,000	220,105
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	10,812
Due after five to ten years	35,656
Due after ten years	350,946
Amortized Cost	397,414	252,484
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	10,818
Due after five to ten years	36,151
Due after ten years	358,833
Fair Value	405,802	250,928
Agency collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	87,305
Debt Securities, Available-for-sale, Amortized Cost	87,305	138,149
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	0
Due after five to ten years	0
Due after ten years	88,511
Debt Securities, Available-for-sale	88,511	134,911
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	293,662
Amortized Cost	293,662	332,775
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	297,314
Fair Value	297,314	326,724
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	0
Due after one year to five years	1,188
Due after five to ten years	189
Due after ten years	0
Debt Securities, Available-for-sale, Amortized Cost	1,377	1,719
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	1,193
Due after five to ten years	203
Due after ten years	0
Debt Securities, Available-for-sale	1,396	1,735
Single issuer trust preferred securities issued by banks [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	488
Debt Securities, Available-for-sale, Amortized Cost	488	717
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	0
Due after five to ten years	0
Due after ten years	493
Debt Securities, Available-for-sale	493	707
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	1,500
Due after ten years	0
Amortized Cost	1,500	1,500
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	1,490
Due after ten years	0
Fair Value	1,490	1,490
Pooled Trust Preferred Securities Issued By Banks And Insurers [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	1,488
Debt Securities, Available-for-sale, Amortized Cost	1,488	1,678
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	0
Due after five to ten years	0
Due after ten years	1,114
Debt Securities, Available-for-sale	1,114	1,329
Small Business Administration Pooled Securities [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	54,024
Debt Securities, Available-for-sale, Amortized Cost	54,024	53,317
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	0
Due after five to ten years	0
Due after ten years	54,795
Debt Securities, Available-for-sale	54,795	51,927
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	31,324
Amortized Cost	31,324	23,727
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	0
Due after five to ten years	0
Due after ten years	31,607
Fair Value	$ 31,607	$ 23,483