Securities - Fair Value and Gross Unrealized Losses by Investment Category and Length of Time (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Debt Securities
Total	$ 243,255
Less than 12 Months	157,662
12 Months or More	85,594
Unrealized Loss, Debt Securities
Total	6,776
Less than 12 Months	2,747
12 Months or More	4,029
Fair Value, Debt and Equity Securities
Total		$ 226,018
Less than 12 Months		137,860
12 Months or More		88,158
Unrealized Loss, Debt and Equity Securities
Total		3,628
Less than 12 Months		1,018
12 Months or More		2,610
Federal agencies and GSEs
Fair Value, Debt Securities
Total	103,732
Less than 12 Months	50,944
12 Months or More	52,789
Unrealized Loss, Debt Securities
Total	3,516
Less than 12 Months	835
12 Months or More	2,681
Fair Value, Debt and Equity Securities
Total		99,133
Less than 12 Months		45,474
12 Months or More		53,659
Unrealized Loss, Debt and Equity Securities
Total		2,127
Less than 12 Months		321
12 Months or More		1,806
Mortgage-backed and CMOs
Fair Value, Debt Securities
Total	99,661
Less than 12 Months	74,839
12 Months or More	24,822
Unrealized Loss, Debt Securities
Total	2,611
Less than 12 Months	1,602
12 Months or More	1,009
Fair Value, Debt and Equity Securities
Total		90,806
Less than 12 Months		64,449
12 Months or More		26,357
Unrealized Loss, Debt and Equity Securities
Total		1,140
Less than 12 Months		533
12 Months or More		607
State and municipal
Fair Value, Debt Securities
Total	38,355
Less than 12 Months	31,395
12 Months or More	6,960
Unrealized Loss, Debt Securities
Total	621
Less than 12 Months	294
12 Months or More	327
Fair Value, Debt and Equity Securities
Total		34,550
Less than 12 Months		27,442
12 Months or More		7,108
Unrealized Loss, Debt and Equity Securities
Total		347
Less than 12 Months		159
12 Months or More		188
Corporate
Fair Value, Debt Securities
Total	1,507
Less than 12 Months	484
12 Months or More	1,023
Unrealized Loss, Debt Securities
Total	28
Less than 12 Months	16
12 Months or More	$ 12
Fair Value, Debt and Equity Securities
Total		1,529
Less than 12 Months		495
12 Months or More		1,034
Unrealized Loss, Debt and Equity Securities
Total		14
Less than 12 Months		5
12 Months or More		$ 9