Investment Securities, Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Security	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)
Investment Securities [Abstract]
Number of investment securities held | Security	491
Less than 12 months, number of positions | Security	164
12 months or more, number of positions | Security	95
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 293,713	$ 229,523	$ 264,391
Less than 12 months, unrealized loss	5,124	1,127	2,092
12 months or more, fair value	112,833	105,991	0
12 months or more, unrealized loss	1,759	1,050	0
Total, fair value	406,546	335,514	264,391
Total, unrealized loss	6,883	2,177	2,092
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	7,654		4,278
Less than 12 months, unrealized loss	56		22
12 months or more, fair value	0		0
12 months or more, unrealized loss	0		0
Total, fair value	7,654		4,278
Total, unrealized loss	56	0	22
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	$ 23,551	94,281	69,433
Less than 12 months, unrealized loss	436	144	300
12 months or more, fair value	59,866	49,883	0
12 months or more, unrealized loss	305	298	0
Total, fair value	83,417	144,164	69,433
Total, unrealized loss	$ 741	442	300
Less than 12 months, number of positions | Security	4
12 months or more, number of positions | Security	4
US Govt SBA [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 10,848	8,379	26,412
Less than 12 months, unrealized loss	82	51	247
12 months or more, fair value	11,737	12,900	0
12 months or more, unrealized loss	179	157	0
Total, fair value	22,585	21,279	26,412
Total, unrealized loss	$ 261	208	247
Less than 12 months, number of positions | Security	66
12 months or more, number of positions | Security	66
Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 259,314	126,863	168,546
Less than 12 months, unrealized loss	4,606	932	1,545
12 months or more, fair value	41,230	43,208	0
12 months or more, unrealized loss	1,275	595	0
Total, fair value	300,544	170,071	168,546
Total, unrealized loss	$ 5,881	1,527	1,545
Less than 12 months, number of positions | Security	75
12 months or more, number of positions | Security	25
Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 7,654		4,278
Less than 12 months, unrealized loss	56		22
12 months or more, fair value	0		0
12 months or more, unrealized loss	0		0
Total, fair value	7,654		4,278
Total, unrealized loss	$ 56	$ 0	$ 22
Less than 12 months, number of positions | Security	19
12 months or more, number of positions | Security	0
Municipal Bonds [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Percentage of bank qualified municipal bond portfolio rated	98.00%
Percentage of portfolio not rated	2.00%