Investment Securities, Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Security	Dec. 31, 2016 USD ($)
Available-for-sale Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months fair value	$ 229,523	$ 250,069
Less than 12 months unrealized loss	1,127	1,905
12 months or more fair value	105,991	0
12 months or more unrealized loss	1,050	0
Total fair value	335,514	250,069
Total unrealized loss	$ 2,177	1,905
Number of investment securities held | Security	476
Less than 12 months, number of positions | Security	97
12 months or more, number of positions | Security	98
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months fair value		7,251
Less than 12 months unrealized loss		40
12 months or more fair value		0
12 months or more unrealized loss		0
Total fair value		7,251
Total unrealized loss		40
US Treasury Notes [Member]
Available-for-sale Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months fair value	$ 94,281	99,429
Less than 12 months unrealized loss	144	332
12 months or more fair value	49,883	0
12 months or more unrealized loss	298	0
Total fair value	144,164	99,429
Total unrealized loss	$ 442	332
Less than 12 months, number of positions | Security	7
12 months or more, number of positions | Security	2
US Govt SBA [Member]
Available-for-sale Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months fair value	$ 8,379	27,483
Less than 12 months unrealized loss	51	260
12 months or more fair value	12,900	0
12 months or more unrealized loss	157	0
Total fair value	21,279	27,483
Total unrealized loss	$ 208	260
Less than 12 months, number of positions | Security	54
12 months or more, number of positions | Security	70
Mortgage Backed Securities [Member]
Available-for-sale Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months fair value	$ 126,863	123,157
Less than 12 months unrealized loss	932	1,313
12 months or more fair value	43,208	0
12 months or more unrealized loss	595	0
Total fair value	170,071	123,157
Total unrealized loss	$ 1,527	1,313
Less than 12 months, number of positions | Security	26
12 months or more, number of positions | Security	36
Government Agency & Government-Sponsored Entities [Member]
Available-for-sale Securities in Continuous Unrealized Loss Position [Abstract]
Total unrealized loss	$ 0	0
Less than 12 months, number of positions | Security	0
12 months or more, number of positions | Security	0
Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months fair value		7,251
Less than 12 months unrealized loss		40
12 months or more fair value		0
12 months or more unrealized loss		0
Total fair value		7,251
Total unrealized loss	$ 0	$ 40
Less than 12 months, number of positions | Security	0
12 months or more, number of positions | Security	0
Municipal Bonds [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Percentage of portfolio rated at either issue or issuer level	99.00%
Percentage of portfolio not rated	1.00%