Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Expected remaining maturities of debt securities available-for-sale, fair value
Fair Value	$ 5,328,492	$ 6,241,117
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Total of debt securities held-to-maturity, amortized cost	3,418,353	2,957,843
Total debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	922,944
Securities available-for-sale, Over 1 year through 5 years, fair value	4,134,681
Securities available-for-sale, Over 5 years through 10 years, fair value	261,860
Securities available-for-sale, Over 10 years, fair value	3,320
Fair Value	5,322,805	6,232,674
Expected remaining maturities of debt securities available-for-sale, amortized cost
Securities available-for-sale, One year or less, amortized cost	919,336
Securities available-for-sale, Over 1 year through 5 years, amortized cost	4,135,324
Securities available-for-sale, Over 5 years through 10 years, amortized cost	265,930
Securities available-for-sale, Over 10 years, amortized cost	3,400
Total of debt securities available-for-sale, amortized cost	5,323,990
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	1,085,642
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	2,030,553
Securities held-to-maturity, Over 10 years, amortized cost	302,158
Total of debt securities held-to-maturity, amortized cost	3,418,353
U.S. Treasury
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	23,194
Securities available-for-sale, Over 1 year through 5 years, fair value	13,064
Fair Value	36,258	35,335
Federal agency - Debt
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	639,733
Securities available-for-sale, Over 1 year through 5 years, fair value	347,513
Securities available-for-sale, Over 5 years through 10 years, fair value	39,270
Fair Value	1,026,516	1,410,536
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	26,000
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	86,170
Securities held-to-maturity, Over 10 years, amortized cost	190,748
Total of debt securities held-to-maturity, amortized cost	302,918	178,413
Federal agency - MBS
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, Over 1 year through 5 years, fair value	105,432
Securities available-for-sale, Over 5 years through 10 years, fair value	17,797
Fair Value	123,229	157,226
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	75,854
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	467,171
Securities held-to-maturity, Over 10 years, amortized cost	11,396
Total of debt securities held-to-maturity, amortized cost	554,421	445,360
CMOs - Federal agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	98,070
Securities available-for-sale, Over 1 year through 5 years, fair value	3,236,456
Securities available-for-sale, Over 5 years through 10 years, fair value	204,793
Fair Value	3,539,319	3,997,298
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	805,601
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	1,077,860
Total of debt securities held-to-maturity, amortized cost	1,883,461	1,781,219
CMOs - Non-agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	2,237
Securities available-for-sale, Over 1 year through 5 years, fair value	24,666
Fair Value	26,903	37,462
State and municipal
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	100,959
Securities available-for-sale, Over 1 year through 5 years, fair value	288,314
Securities available-for-sale, Over 10 years, fair value	3,320
Fair Value	392,593	415,995
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	80,107
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	399,352
Securities held-to-maturity, Over 10 years, amortized cost	100,014
Total of debt securities held-to-maturity, amortized cost	579,473	454,155
Other debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	58,751
Securities available-for-sale, Over 1 year through 5 years, fair value	119,236
Fair Value	177,987	178,822
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	98,080
Total of debt securities held-to-maturity, amortized cost	$ 98,080	$ 98,696