Investment Securities, Available-for-sale Securities, Gross Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	$ 273,882	$ 577,164
12 months or more - Fair Value	270,920	18,653
Total - Fair Value	544,802	595,817
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	2,355	10,717
12 months or more - Gross Unrealized Loss	3,719	684
Total - Gross Unrealized Loss	6,074	11,401
U. S. Government Sponsored Enterprises [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	24,887	102,266
12 months or more - Fair Value	88,544	0
Total - Fair Value	113,431	102,266
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	113	2,621
12 months or more - Gross Unrealized Loss	1,346	0
Total - Gross Unrealized Loss	1,459	2,621
Corporate Bonds [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	0	40,705
12 months or more - Fair Value	40,381	0
Total - Fair Value	40,381	40,705
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	0	251
12 months or more - Gross Unrealized Loss	61	0
Total - Gross Unrealized Loss	61	251
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	228,925	359,622
12 months or more - Fair Value	82,423	4,713
Total - Fair Value	311,348	364,335
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	1,972	5,766
12 months or more - Gross Unrealized Loss	1,180	117
Total - Gross Unrealized Loss	3,152	5,883
Small Business Administration-Guaranteed Participation Securities [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	20,070	64,560
12 months or more - Fair Value	49,748	13,940
Total - Fair Value	69,818	78,500
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	270	1,960
12 months or more - Gross Unrealized Loss	1,081	567
Total - Gross Unrealized Loss	1,351	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	0	10,011
12 months or more - Fair Value	9,824	0
Total - Fair Value	9,824	10,011
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	0	119
12 months or more - Gross Unrealized Loss	51	0
Total - Gross Unrealized Loss	$ 51	$ 119