Securities - Securities Sold (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	$ 495,192
Net Proceeds	495,340	$ 4,028	$ 8,444
Gain/(Loss)	148
Trust preferred securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	9,346
Net Proceeds	9,403
Gain/(Loss)	57
Other debt securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	7,269
Net Proceeds	7,395
Gain/(Loss)	126
Obligations of other U.S. Government agencies and corporations
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	11,088
Net Proceeds	10,974
Gain/(Loss)	(114)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	110,019
Net Proceeds	112,199
Gain/(Loss)	2,180
Government agency mortgage backed securities | Residential mortgage backed securities:
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	264,924
Net Proceeds	263,217
Gain/(Loss)	(1,707)
Government agency mortgage backed securities | Commercial mortgage backed securities:
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	14,104
Net Proceeds	14,082
Gain/(Loss)	(22)
Government agency collateralized mortgage obligations | Residential mortgage backed securities:
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	72,153
Net Proceeds	71,781
Gain/(Loss)	(372)
Government agency collateralized mortgage obligations | Commercial mortgage backed securities:
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	6,289
Net Proceeds	6,289
Gain/(Loss)	$ 0