Investment Securities, Amortized Cost, Fair Values, and Unrealized Gains and Losses of Securities (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		$ 482,757	$ 448,282
Gross unrealized gains		1,016	1,886
Gross unrealized losses		2,177	1,905
Fair/Book value		481,596	448,263
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Book value		54,460	58,109
Gross unrealized gains		776	339
Gross unrealized losses		0	40
Fair value		55,236	58,408
Government Agency & Government-Sponsored Entities [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		3,080	3,127
Gross unrealized gains		48	114
Gross unrealized losses		0	0
Fair/Book value		3,128	3,241
US Treasury Notes [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		144,606	134,755
Gross unrealized gains		0	5
Gross unrealized losses		442	332
Fair/Book value		144,164	134,428
US Govt SBA [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		29,559	36,532
Gross unrealized gains		29	42
Gross unrealized losses		208	260
Fair/Book value		29,380	36,314
Mortgage Backed Securities [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost	[1]	302,502	272,858
Gross unrealized gains	[1]	939	1,725
Gross unrealized losses	[1]	1,527	1,313
Fair/Book value	[1]	301,914	273,270
Other [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		3,010	1,010
Gross unrealized gains		0	0
Gross unrealized losses		0	0
Fair/Book value		3,010	1,010
Obligations of States and Political Subdivisions [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Book value		54,460	58,109
Gross unrealized gains		776	339
Gross unrealized losses		0	40
Fair value		$ 55,236	$ 58,408

[1] All Mortgage Backed Securities were issued by an agency or government sponsored entity of the U.S. government.