Investment Securities, Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) Security	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Investment Securities, Qualitative Disclosure [Abstract]
Number of investment securities held | Security	588
Less than 12 months, number of positions | Security	26
12 months or more, number of positions | Security	133
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 156,706	$ 180,524	$ 293,713
Less than 12 months, unrealized loss	53	563	5,124
12 months or more, fair value	206,184	255,418	112,833
12 months or more, unrealized loss	1,767	4,888	1,759
Total, fair value	362,890	435,942	406,546
Total, unrealized loss	1,820	5,451	6,883
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	229	6,052	7,654
Less than 12 months, unrealized loss	1	23	56
12 months or more, fair value	360	849	0
12 months or more, unrealized loss	0	16	0
Total, fair value	589	6,901	7,654
Total, unrealized loss	1	39	56
Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	229	6,052	7,654
Less than 12 months, unrealized loss	1	23	56
12 months or more, fair value	360	849	0
12 months or more, unrealized loss	0	16	0
Total, fair value	589	6,901	7,654
Total, unrealized loss	$ 1	39	56
Less than 12 months, number of positions | Security	1
12 months or more, number of positions | Security	1
Municipal Bonds [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Percentage of bank qualified municipal bond portfolio rated	99.00%
Percentage of portfolio not rated	1.00%
Government Agency & Government-Sponsored Entities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Total, unrealized loss	$ 0	0	0
Less than 12 months, number of positions | Security	0
12 months or more, number of positions | Security	0
US Treasury Notes [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 149,962	124,985	23,551
Less than 12 months, unrealized loss	28	7	436
12 months or more, fair value	4,909	39,529	59,866
12 months or more, unrealized loss	6	151	305
Total, fair value	154,871	164,514	83,417
Total, unrealized loss	$ 34	158	741
Less than 12 months, number of positions | Security	15
12 months or more, number of positions | Security	1
US Govt SBA [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 1,310	3,250	10,848
Less than 12 months, unrealized loss	0	28	82
12 months or more, fair value	10,823	8,618	11,737
12 months or more, unrealized loss	147	132	179
Total, fair value	12,133	11,868	22,585
Total, unrealized loss	$ 147	160	261
Less than 12 months, number of positions | Security	4
12 months or more, number of positions | Security	68
Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 5,434	52,289	259,314
Less than 12 months, unrealized loss	25	528	4,606
12 months or more, fair value	190,452	207,271	41,230
12 months or more, unrealized loss	1,614	4,605	1,275
Total, fair value	195,886	259,560	300,544
Total, unrealized loss	$ 1,639	$ 5,133	$ 5,881
Less than 12 months, number of positions | Security	6
12 months or more, number of positions | Security	63