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Contractural maturities (Details 3) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
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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

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