Securities - Unrealized Loss Positions (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) security	Dec. 31, 2015 USD ($)
Fair value
Less Than 12 Months, Fair Value	$ 92,173,000	$ 41,772,000
12 Months or More, Fair Value	2,562,000	15,889,000
Total Fair Value	94,735,000	57,661,000
Unrealized Loss
Less Than 12 Months, Unrealized Loss	1,318,000	498,000
12 Months or More, Unrealized Loss	42,000	284,000
Total Unrealized Loss	$ 1,360,000	782,000
Other information
Number of positions considered temporarily impaired | security	156
Other than temporary impairment	$ 0
U.S. government agencies and corporations
Fair value
Less Than 12 Months, Fair Value	16,111,000	9,530,000
12 Months or More, Fair Value		8,971,000
Total Fair Value	16,111,000	18,501,000
Unrealized Loss
Less Than 12 Months, Unrealized Loss	414,000	69,000
12 Months or More, Unrealized Loss		189,000
Total Unrealized Loss	414,000	258,000
Mortgage-backed securities
Fair value
Less Than 12 Months, Fair Value	54,227,000	27,085,000
12 Months or More, Fair Value	671,000	2,252,000
Total Fair Value	54,898,000	29,337,000
Unrealized Loss
Less Than 12 Months, Unrealized Loss	621,000	397,000
12 Months or More, Unrealized Loss	1,000	46,000
Total Unrealized Loss	622,000	443,000
Obligations of states and political subdivisions
Fair value
Less Than 12 Months, Fair Value	21,835,000	5,157,000
12 Months or More, Fair Value	1,891,000	4,666,000
Total Fair Value	23,726,000	9,823,000
Unrealized Loss
Less Than 12 Months, Unrealized Loss	283,000	32,000
12 Months or More, Unrealized Loss	41,000	49,000
Total Unrealized Loss	$ 324,000	$ 81,000
Standard & Poor's, A Rating | U.S. government agencies and corporations
Other information
Percentage of portfolio with rating	97.00%
Percentage of portfolio with rating in an unrealized loss positions	97.00%
Not A Rating Or Better | U.S. government agencies and corporations
Other information
Percentage of portfolio with rating in an unrealized loss positions	3.00%