Investment Securities, Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-Sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 160,528	$ 110,869
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	8,106	3,085
Held-to-Maturity:
Less than 12 Months, Fair Value	14,730	9,824
Less than 12 Months, Unrealized Losses	635	133
12 Months or More, Fair Value	9,313	6,747
12 Months or More, Unrealized Losses	417	189
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	76,168	107,759
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,234	939
U.S. Treasury notes [Member]
Available-for-Sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,236	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	58	0
Held-to-Maturity:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	948	2,259
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	37	24
U.S. Agency notes [Member]
Available-for-Sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	67,492	44,560
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,363	1,289
Held-to-Maturity:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	9,680	33,651
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	203	344
U.S. Agency mortgage-backed securities [Member]
Available-for-Sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	51,948	41,080
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,862	1,085
Held-to-Maturity:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,527	24,433
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	88	142
Non-taxable Municipal securities [Member]
Available-for-Sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	30,890	24,197
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,599	703
Held-to-Maturity:
Less than 12 Months, Fair Value	14,331	9,824
Less than 12 Months, Unrealized Losses	634	133
12 Months or More, Fair Value	6,237	3,542
12 Months or More, Unrealized Losses	193	94
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	52,974	36,348
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	741	315
Taxable Municipal securities [Member]
Available-for-Sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	8,962	1,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	224	8
Held-to-Maturity:
Less than 12 Months, Fair Value	399	0
Less than 12 Months, Unrealized Losses	1	0
12 Months or More, Fair Value	3,076	3,205
12 Months or More, Unrealized Losses	224	95
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	8,039	11,068
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 165	$ 114