Investment Securities, Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available-for-Sale:
Less than 12 Months, Fair Value	$ 131,816	$ 107,759
Less than 12 Months, Unrealized Losses	2,343	939
12 Months or More, Fair Value	107,435	110,869
12 Months or More, Unrealized Losses	5,125	3,085
Held-to-Maturity:
Less than 12 Months, Fair Value	17,757	9,824
Less than 12 Months, Unrealized Losses	514	133
12 Months or More, Fair Value	6,639	6,747
12 Months or More, Unrealized Losses	297	189
U.S. Treasury notes [Member]
Available-for-Sale:
Less than 12 Months, Fair Value	2,218	2,259
Less than 12 Months, Unrealized Losses	63	24
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
U.S. Agency notes [Member]
Available-for-Sale:
Less than 12 Months, Fair Value	33,216	33,651
Less than 12 Months, Unrealized Losses	778	344
12 Months or More, Fair Value	43,696	44,560
12 Months or More, Unrealized Losses	2,122	1,289
U.S. Agency mortgage-backed securities [Member]
Available-for-Sale:
Less than 12 Months, Fair Value	23,495	24,433
Less than 12 Months, Unrealized Losses	462	142
12 Months or More, Fair Value	38,760	41,080
12 Months or More, Unrealized Losses	1,750	1,085
Non-taxable Municipal securities [Member]
Available-for-Sale:
Less than 12 Months, Fair Value	57,079	36,348
Less than 12 Months, Unrealized Losses	815	315
12 Months or More, Fair Value	23,598	24,197
12 Months or More, Unrealized Losses	1,235	703
Held-to-Maturity:
Less than 12 Months, Fair Value	17,357	9,824
Less than 12 Months, Unrealized Losses	514	133
12 Months or More, Fair Value	3,535	3,542
12 Months or More, Unrealized Losses	100	94
Taxable Municipal securities [Member]
Available-for-Sale:
Less than 12 Months, Fair Value	15,808	11,068
Less than 12 Months, Unrealized Losses	225	114
12 Months or More, Fair Value	1,381	1,032
12 Months or More, Unrealized Losses	18	8
Held-to-Maturity:
Less than 12 Months, Fair Value	400	0
Less than 12 Months, Unrealized Losses	0	0
12 Months or More, Fair Value	3,104	3,205
12 Months or More, Unrealized Losses	$ 197	$ 95