Investment Securities Held-to-maturity Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Held-to-maturity Securities
Amortized Cost	$ 40,928,000	$ 43,144,000
Gross Unrealized Gains	876,000	653,000
Gross Unrealized Losses	591,000	570,000
Fair Value	41,213,000	43,227,000
Gross realized gains or losses	0	0	$ 0
States and political subdivisions
Schedule of Held-to-maturity Securities
Amortized Cost	3,810,000	3,820,000
Gross Unrealized Gains	607,000	221,000
Gross Unrealized Losses	0	0
Fair Value	4,417,000	4,041,000
Residential mortgage-backed securities
Schedule of Held-to-maturity Securities
Amortized Cost	32,487,000	33,858,000
Gross Unrealized Gains	269,000	432,000
Gross Unrealized Losses	529,000	528,000
Fair Value	32,227,000	33,762,000
Commercial mortgage-backed securities
Schedule of Held-to-maturity Securities
Amortized Cost	4,631,000	5,466,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	62,000	42,000
Fair Value	$ 4,569,000	$ 5,424,000