Securities (Details 2) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Securities
Securities pledged to secure trust funds, public deposits, or for other purposes required or permitted by law	$ 1,050,000,000
Expected remaining maturities of debt securities available-for-sale, fair value
Fair Value	9,205,989,000	7,571,901,000
Securities pledged with right by contract or custom to sell or repledge	48,697,000	37,861,000
Total debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	2,150,489,000
Securities available-for-sale, Over 1 year through 5 years, fair value	6,516,786,000
Securities available-for-sale, Over 5 years through 10 years, fair value	513,031,000
Securities available-for-sale, Over 10 years, fair value	23,982,000
Fair Value	9,204,288,000	7,570,674,000
Expected remaining maturities of debt securities available-for-sale, amortized cost
Securities available-for-sale, One year or less, amortized cost	2,144,654,000
Securities available-for-sale, Over 1 year through 5 years, amortized cost	6,410,472,000
Securities available-for-sale, Over 5 years through 10 years, amortized cost	477,855,000
Securities available-for-sale, Over 10 years, amortized cost	23,921,000
Total of debt securities available-for-sale, amortized cost	9,056,902,000
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	140,646,000
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	1,115,002,000
Securities held-to-maturity, Over 10 years, amortized cost	142,755,000
Total of debt securities held-to-maturity, amortized cost	1,398,403,000
U.S. Treasury
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, Over 1 year through 5 years, fair value	20,397,000
Fair Value	20,397,000	19,182,000
Federal agency - Debt
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	1,809,346,000
Securities available-for-sale, Over 1 year through 5 years, fair value	539,856,000
Fair Value	2,349,202,000	1,973,862,000
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 10 years, amortized cost	97,183,000
Total of debt securities held-to-maturity, amortized cost	97,183,000
Federal agency - MBS
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	4,000
Securities available-for-sale, Over 1 year through 5 years, fair value	441,236,000
Securities available-for-sale, Over 5 years through 10 years, fair value	251,792,000
Fair Value	693,032,000	681,044,000
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	2,453,000
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	301,189,000
Total of debt securities held-to-maturity, amortized cost	303,642,000
CMOs - Federal agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	226,935,000
Securities available-for-sale, Over 1 year through 5 years, fair value	4,925,990,000
Securities available-for-sale, Over 5 years through 10 years, fair value	165,328,000
Fair Value	5,318,253,000	4,326,907,000
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	123,436,000
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	622,544,000
Total of debt securities held-to-maturity, amortized cost	745,980,000
CMOs - Non-agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	8,344,000
Securities available-for-sale, Over 1 year through 5 years, fair value	33,336,000
Securities available-for-sale, Over 5 years through 10 years, fair value	19,833,000
Fair Value	61,513,000	69,001,000
State and municipal
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	90,659,000
Securities available-for-sale, Over 1 year through 5 years, fair value	266,203,000
Securities available-for-sale, Over 5 years through 10 years, fair value	73,630,000
Securities available-for-sale, Over 10 years, fair value	23,982,000
Fair Value	454,474,000	401,604,000
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	14,757,000
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	191,269,000
Securities held-to-maturity, Over 10 years, amortized cost	45,572,000
Total of debt securities held-to-maturity, amortized cost	251,598,000
Other debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	15,201,000
Securities available-for-sale, Over 1 year through 5 years, fair value	289,768,000
Securities available-for-sale, Over 5 years through 10 years, fair value	2,448,000
Fair Value	$ 307,417,000	$ 99,074,000