Investment Securities, Available-for-sale Securities, Gross Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	$ 519,159	$ 577,164
12 months or more - Fair Value	38,765	18,653
Total - Fair Value	557,924	595,817
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	6,335	10,717
12 months or more - Gross Unrealized Loss	669	684
Total - Gross Unrealized Loss	7,004	11,401
U. S. Government Sponsored Enterprises [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	88,286	102,266
12 months or more - Fair Value	14,978	0
Total - Fair Value	103,264	102,266
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	1,602	2,621
12 months or more - Gross Unrealized Loss	22	0
Total - Gross Unrealized Loss	1,624	2,621
Mortgage Backed Securities and Collateralized Mortgage Obligations-Residential [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	320,377	359,622
12 months or more - Fair Value	11,024	4,713
Total - Fair Value	331,401	364,335
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	3,361	5,766
12 months or more - Gross Unrealized Loss	191	117
Total - Gross Unrealized Loss	3,552	5,883
Corporate Bonds [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	40,498	40,705
12 months or more - Fair Value	0	0
Total - Fair Value	40,498	40,705
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	115	251
12 months or more - Gross Unrealized Loss	0	0
Total - Gross Unrealized Loss	115	251
Small Business Administration-Guaranteed Participation Securities [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	60,095	64,560
12 months or more - Fair Value	12,763	13,940
Total - Fair Value	72,858	78,500
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	1,200	1,960
12 months or more - Gross Unrealized Loss	456	567
Total - Gross Unrealized Loss	1,656	2,527
Mortgage Backed Securities and Collateralized Mortgage Obligations-Commercial [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	9,903	10,011
12 months or more - Fair Value	0	0
Total - Fair Value	9,903	10,011
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	57	119
12 months or more - Gross Unrealized Loss	0	0
Total - Gross Unrealized Loss	$ 57	$ 119