Contractural maturities (Details 3) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available for Sale, Fair Value
Debt Securities, Available-for-sale, Amortized Cost	$ 450,548
Debt Securities, Available-for-sale	442,752	$ 447,498
Held to Maturity, Amortized Cost
Amortized Cost	611,490	497,688
Held to Maturity, Fair Value
Fair Value	603,640	494,194
U.S. Government agency 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	20,010
Due after five to ten years	12,467
Due after ten years	0
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	19,903
Due after five to ten years	12,135
Due after ten years	0
Debt Securities, Available-for-sale, Amortized Cost	32,477	35,475
Debt Securities, Available-for-sale	32,038	35,430
Debt Securities [Member]
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	89
Due after one year to five years	73,232
Due after five to ten years	102,824
Due after ten years	274,403
Available for Sale, Fair Value
Due in one year or less	90
Due in one year or less	72,435
Due after five to ten years	101,501
Due after ten years	268,726
Securities - available for sale	442,752
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	13,102
Due after five to ten years	37,938
Due after ten years	560,450
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	12,981
Due after five to ten years	37,532
Due after ten years	553,127
Fair Value	603,640
US Treasury Securities [Member]
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	1,004
Due after five to ten years	0
Due after ten years	0
Amortized Cost	1,004	1,006
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	1,015
Due after five to ten years	0
Due after ten years	0
Fair Value	1,015	1,035
Agency mortgage-backed securities
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Due in one year or less	89
Due after one year to five years	52,452
Due after five to ten years	89,408
Due after ten years	80,542
Available for Sale, Fair Value
Due in one year or less	90
Due in one year or less	51,761
Due after five to ten years	88,402
Due after ten years	79,852
Debt Securities, Available-for-sale, Amortized Cost	222,491	214,934
Debt Securities, Available-for-sale	220,105	215,764
Held to Maturity, Amortized Cost
Due in one year or less	0
Due after one year to five years	12,098
Due after five to ten years	35,703
Due after ten years	204,683
Amortized Cost	252,484	204,768
Held to Maturity, Fair Value
Due in one year or less	0
Due after one year to five years	11,966
Due after five to ten years	35,310
Due after ten years	203,652
Fair Value	250,928	205,823
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	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	134,911
Debt Securities, Available-for-sale, Amortized Cost	138,149	124,098
Debt Securities, Available-for-sale	134,911	122,012
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	735
Due after ten years	332,040
Amortized Cost	332,775	262,998
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	732
Due after ten years	325,992
Fair Value	326,724	258,408
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	770
Due after five to ten years	949
Due after ten years	0
Available for Sale, Fair Value
Due in one year or less	0
Due in one year or less	771
Due after five to ten years	964
Due after ten years	0
Debt Securities, Available-for-sale, Amortized Cost	1,719	2,237
Debt Securities, Available-for-sale	1,735	2,274
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	0
Amortized Cost	0
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	0
Fair Value	0
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	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	707
Debt Securities, Available-for-sale, Amortized Cost	717	2,012
Debt Securities, Available-for-sale	707	2,016
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	1,529
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	1,678
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	1,329
Debt Securities, Available-for-sale, Amortized Cost	1,678	2,179
Debt Securities, Available-for-sale	1,329	1,640
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	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	51,927
Debt Securities, Available-for-sale, Amortized Cost	53,317	47,852
Debt Securities, Available-for-sale	51,927	47,778
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	23,727
Amortized Cost	23,727	27,416
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	23,483
Fair Value	$ 23,483	$ 27,399