Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Expected remaining maturities of debt securities available-for-sale, fair value
Fair Value	$ 5,386,754	$ 6,241,117
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Total of debt securities held-to-maturity, amortized cost	3,202,997	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	597,056
Securities available-for-sale, Over 1 year through 5 years, fair value	4,371,937
Securities available-for-sale, Over 5 years through 10 years, fair value	403,902
Securities available-for-sale, Over 10 years, fair value	3,319
Fair Value	5,376,214	6,232,674
Expected remaining maturities of debt securities available-for-sale, amortized cost
Securities available-for-sale, One year or less, amortized cost	594,486
Securities available-for-sale, Over 1 year through 5 years, amortized cost	4,385,520
Securities available-for-sale, Over 5 years through 10 years, amortized cost	409,872
Securities available-for-sale, Over 10 years, amortized cost	3,400
Total of debt securities available-for-sale, amortized cost	5,393,278
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	1,434
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	847,521
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	2,011,515
Securities held-to-maturity, Over 10 years, amortized cost	342,527
Total of debt securities held-to-maturity, amortized cost	3,202,997
U.S. Treasury
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less, fair value	172,234
Securities available-for-sale, Over 1 year through 5 years, fair value	13,079
Fair Value	185,313	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	215,510
Securities available-for-sale, Over 1 year through 5 years, fair value	499,012
Securities available-for-sale, Over 5 years through 10 years, fair value	39,167
Fair Value	753,689	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	11,082
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	57,513
Securities held-to-maturity, Over 10 years, amortized cost	196,476
Total of debt securities held-to-maturity, amortized cost	265,071	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	107,729
Securities available-for-sale, Over 5 years through 10 years, fair value	17,884
Fair Value	125,613	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	54,660
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	377,913
Securities held-to-maturity, Over 10 years, amortized cost	17,761
Total of debt securities held-to-maturity, amortized cost	450,334	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	98,666
Securities available-for-sale, Over 1 year through 5 years, fair value	3,244,429
Securities available-for-sale, Over 5 years through 10 years, fair value	346,851
Fair Value	3,689,946	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	648,349
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	1,218,750
Total of debt securities held-to-maturity, amortized cost	1,867,099	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	2,500
Securities available-for-sale, Over 1 year through 5 years, fair value	33,848
Fair Value	36,348	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	78,801
Securities available-for-sale, Over 1 year through 5 years, fair value	324,777
Securities available-for-sale, Over 10 years, fair value	3,319
Fair Value	406,897	415,995
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	1,434
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	35,041
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	357,339
Securities held-to-maturity, Over 10 years, amortized cost	128,290
Total of debt securities held-to-maturity, amortized cost	522,104	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	29,345
Securities available-for-sale, Over 1 year through 5 years, fair value	149,063
Fair Value	178,408	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	98,389
Total of debt securities held-to-maturity, amortized cost	$ 98,389	$ 98,696