Investment Securities AFS and HTM Gross Unrealized Losses (Details) $ in Thousands	Jun. 30, 2015 USD ($) security	Dec. 31, 2014 USD ($) security
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (11,818)	$ (3,189)
Unrealized losses on available for sale securities, 12 months or more	(25,007)	(53,343)
Total unrealized losses on available for sale securities	(36,825)	(56,532)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,883,127	669,839
Fair value of unrealized losses on available for sale securities, 12 months or more	834,005	1,719,118
Total fair value of unrealized losses on available for sale securities	2,717,132	2,388,957
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	(5,824)	(216)
Unrealized losses on held to maturity securities, 12 months or more	(464)	(616)
Total unrealized losses on held to maturity securities	(6,288)	(832)
Fair value of unrealized losses on held to maturity securities, less than 12 months	303,766	31,924
Fair value of unrealized losses on held to maturity securities, 12 months or more	9,346	38,915
Total fair value of unrealized losses on held to maturity securities	313,112	70,839
US Treasury Securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months		(1)
Unrealized losses on available for sale securities, 12 months or more		0
Total unrealized losses on available for sale securities		(1)
Fair value of unrealized losses on available for sale securities, less than 12 months		998
Fair value of unrealized losses on available for sale securities, 12 months or more		0
Total fair value of unrealized losses on available for sale securities		$ 998
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security		1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security		0
Obligations of state and political subdivisions (municipal securities) [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	(47)	$ (9)
Unrealized losses on available for sale securities, 12 months or more	(3)	(20)
Total unrealized losses on available for sale securities	(50)	(29)
Fair value of unrealized losses on available for sale securities, less than 12 months	8,022	3,374
Fair value of unrealized losses on available for sale securities, 12 months or more	186	2,133
Total fair value of unrealized losses on available for sale securities	$ 8,208	$ 5,507
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	18	6
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	1	6
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (5,824)	$ (216)
Unrealized losses on held to maturity securities, 12 months or more	(464)	(616)
Total unrealized losses on held to maturity securities	(6,288)	(832)
Fair value of unrealized losses on held to maturity securities, less than 12 months	303,766	31,924
Fair value of unrealized losses on held to maturity securities, 12 months or more	9,346	38,915
Total fair value of unrealized losses on held to maturity securities	$ 313,112	$ 70,839
Obligations of state and political subdivisions (municipal securities) [Member] | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	623	74
Obligations of state and political subdivisions (municipal securities) [Member] | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	21	85
Government National Mortgage Association (GNMA) [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (6,719)	$ (1,404)
Unrealized losses on available for sale securities, 12 months or more	(6,519)	(29,146)
Total unrealized losses on available for sale securities	(13,238)	(30,550)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,015,136	333,713
Fair value of unrealized losses on available for sale securities, 12 months or more	387,416	1,256,533
Total fair value of unrealized losses on available for sale securities	$ 1,402,552	$ 1,590,246
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	62	16
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	20	56
Private Label [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (9)	$ (9)
Unrealized losses on available for sale securities, 12 months or more	(1)	(1)
Total unrealized losses on available for sale securities	(10)	(10)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,825	1,772
Fair value of unrealized losses on available for sale securities, 12 months or more	21	27
Total fair value of unrealized losses on available for sale securities	$ 1,846	$ 1,799
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	2	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	2	2
GNMA commercial mortgage-related securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (5,043)	$ (1,766)
Unrealized losses on available for sale securities, 12 months or more	(18,484)	(24,176)
Total unrealized losses on available for sale securities	(23,527)	(25,942)
Fair value of unrealized losses on available for sale securities, less than 12 months	858,144	329,982
Fair value of unrealized losses on available for sale securities, 12 months or more	446,382	460,425
Total fair value of unrealized losses on available for sale securities	$ 1,304,526	$ 790,407
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	29	9
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	20	20