Investment Securities, Available-for-sale Securities, Gross Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	$ 109,786	$ 778,568
12 months or more - Fair Value	505,447	54,835
Total - Fair Value	615,233	833,403
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	736	28,184
12 months or more - Gross Unrealized Loss	12,907	2,350
Total - Gross Unrealized Loss	13,643	30,534
U. S. government sponsored enterprises [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	27,422	198,023
12 months or more - Fair Value	54,863	0
Total - Fair Value	82,285	198,023
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	98	1,724
12 months or more - Gross Unrealized Loss	637	0
Total - Gross Unrealized Loss	735	1,724
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	81,269	466,056
12 months or more - Fair Value	339,676	54,835
Total - Fair Value	420,945	520,891
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	630	17,698
12 months or more - Gross Unrealized Loss	6,983	2,350
Total - Gross Unrealized Loss	7,613	20,048
Corporate bonds [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	501	902
12 months or more - Fair Value	0	0
Total - Fair Value	501	902
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	2	1
12 months or more - Gross Unrealized Loss	0	0
Total - Gross Unrealized Loss	2	1
Small Business Administration-guaranteed participation securities [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	0	103,029
12 months or more - Fair Value	100,491	0
Total - Fair Value	100,491	103,029
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	0	8,354
12 months or more - Gross Unrealized Loss	4,939	0
Total - Gross Unrealized Loss	4,939	8,354
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	10,558
12 months or more - Fair Value	10,417	0
Total - Fair Value	10,417	10,558
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	0	407
12 months or more - Gross Unrealized Loss	348	0
Total - Gross Unrealized Loss	348	407
Other [Member]
Available for sale securities unrealized loss position - Fair Value [Abstract]
Less than 12 months - Fair Value	594
12 months or more - Fair Value	0
Total - Fair Value	594
Available for sale securities unrealized loss position - Gross Unrealized Loss [Abstract]
Less than 12 months - Gross Unrealized Loss	6
12 months or more - Gross Unrealized Loss	0
Total - Gross Unrealized Loss	$ 6