Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Expected remaining maturities of debt securities available-for-sale, fair value
Fair Value	$ 6,895,130	$ 9,205,989
Total debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	510,393
Securities available-for-sale, Over 1 year through 5 years, fair value	5,081,607
Securities available-for-sale, Over 5 years through 10 years, fair value	1,289,387
Securities available-for-sale, Over 10 years, fair value	7,696
Fair Value	6,889,083	9,204,288
Expected remaining maturities of debt securities available-for-sale, amortized cost
Securities available-for-sale, One year or less, amortized cost	507,840
Securities available-for-sale, Over 1 year through 5 years, amortized cost	5,082,693
Securities available-for-sale, Over 5 years through 10 years, amortized cost	1,314,292
Securities available-for-sale, Over 10 years, amortized cost	7,769
Total of debt securities available-for-sale, amortized cost	6,912,594
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	659
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	212,118
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	1,210,746
Securities held-to-maturity, Over 10 years, amortized cost	225,997
Total of debt securities held-to-maturity, amortized cost	1,649,520
U.S. Treasury
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	12,078
Securities available-for-sale, Over 1 year through 5 years, fair value	23,347
Fair Value	35,425	20,397
Federal agency - Debt
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	317,377
Securities available-for-sale, Over 1 year through 5 years, fair value	625,652
Securities available-for-sale, Over 5 years through 10 years, fair value	59,418
Fair Value	1,002,447	2,349,202
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	7,000
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	60,022
Securities held-to-maturity, Over 10 years, amortized cost	72,998
Total of debt securities held-to-maturity, amortized cost	140,020
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	68,967
Securities available-for-sale, Over 5 years through 10 years, fair value	128,206
Fair Value	197,173	693,032
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	14,646
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	340,827
Securities held-to-maturity, Over 10 years, amortized cost	4,479
Total of debt securities held-to-maturity, amortized cost	359,952
CMOs - Federal agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	128,236
Securities available-for-sale, Over 1 year through 5 years, fair value	3,706,036
Securities available-for-sale, Over 5 years through 10 years, fair value	908,312
Fair Value	4,742,584	5,318,253
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	181,723
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	667,877
Total of debt securities held-to-maturity, amortized cost	849,600
CMOs - Non-agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	111
Securities available-for-sale, Over 1 year through 5 years, fair value	9,218
Securities available-for-sale, Over 5 years through 10 years, fair value	33,983
Fair Value	43,312	61,513
State and municipal
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	39,865
Securities available-for-sale, Over 1 year through 5 years, fair value	355,575
Securities available-for-sale, Over 5 years through 10 years, fair value	72,650
Securities available-for-sale, Over 10 years, fair value	7,696
Fair Value	475,786	454,474
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	659
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	8,749
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	142,020
Securities held-to-maturity, Over 10 years, amortized cost	148,520
Total of debt securities held-to-maturity, amortized cost	299,948
Other debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	12,726
Securities available-for-sale, Over 1 year through 5 years, fair value	292,812
Securities available-for-sale, Over 5 years through 10 years, fair value	86,818
Fair Value	$ 392,356	$ 307,417