Securities - Fair Value and Gross Unrealized Losses by Investment Category and Length of Time (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Debt Securities
Total	$ 259,782
Less than 12 Months	109,356
12 Months or More	150,426
Unrealized Loss, Debt Securities
Total	9,495
Less than 12 Months	1,716
12 Months or More	7,779
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	112,168
Less than 12 Months	34,414
12 Months or More	77,754
Unrealized Loss, Debt Securities
Total	4,991
Less than 12 Months	469
12 Months or More	4,522
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	95,154
Less than 12 Months	36,050
12 Months or More	59,104
Unrealized Loss, Debt Securities
Total	3,554
Less than 12 Months	840
12 Months or More	2,714
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	51,631
Less than 12 Months	38,892
12 Months or More	12,739
Unrealized Loss, Debt Securities
Total	928
Less than 12 Months	407
12 Months or More	521
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	829
Less than 12 Months	0
12 Months or More	829
Unrealized Loss, Debt Securities
Total	22
Less than 12 Months	0
12 Months or More	$ 22
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