Investment Securities, Available-for-sale Securities, Gross Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	$ 600,173	$ 577,164
12 months or more - Fair Value	18,421	18,653
Total - Fair Value	618,594	595,817
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	9,578	10,717
12 months or more - Gross Unrealized Loss	658	684
Total - Gross Unrealized Loss	10,236	11,401
U. S. Government Sponsored Enterprises [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	142,187	102,266
12 months or more - Fair Value	0	0
Total - Fair Value	142,187	102,266
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	2,689	2,621
12 months or more - Gross Unrealized Loss	0	0
Total - Gross Unrealized Loss	2,689	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	345,977	359,622
12 months or more - Fair Value	4,466	4,713
Total - Fair Value	350,443	364,335
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	5,004	5,766
12 months or more - Gross Unrealized Loss	110	117
Total - Gross Unrealized Loss	5,114	5,883
Corporate Bonds [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	40,612	40,705
12 months or more - Fair Value	0	0
Total - Fair Value	40,612	40,705
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	173	251
12 months or more - Gross Unrealized Loss	0	0
Total - Gross Unrealized Loss	173	251
Small Business Administration-Guaranteed Participation Securities [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	61,474	64,560
12 months or more - Fair Value	13,955	13,940
Total - Fair Value	75,429	78,500
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	1,590	1,960
12 months or more - Gross Unrealized Loss	548	567
Total - Gross Unrealized Loss	2,138	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	9,923	10,011
12 months or more - Fair Value	0	0
Total - Fair Value	9,923	10,011
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	122	119
12 months or more - Gross Unrealized Loss	0	0
Total - Gross Unrealized Loss	$ 122	$ 119