Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Expected remaining maturities of debt securities available-for-sale, fair value
Fair Value	$ 7,044,571	$ 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	462,183
Securities available-for-sale, Over 1 year through 5 years, fair value	5,034,283
Securities available-for-sale, Over 5 years through 10 years, fair value	1,517,668
Securities available-for-sale, Over 10 years, fair value	25,302
Fair Value	7,039,436	9,204,288
Expected remaining maturities of debt securities available-for-sale, amortized cost
Securities available-for-sale, One year or less, amortized cost	459,740
Securities available-for-sale, Over 1 year through 5 years, amortized cost	5,015,064
Securities available-for-sale, Over 5 years through 10 years, amortized cost	1,532,327
Securities available-for-sale, Over 10 years, amortized cost	25,782
Total of debt securities available-for-sale, amortized cost	7,032,913
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	152,949
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	1,119,108
Securities held-to-maturity, Over 10 years, amortized cost	231,916
Total of debt securities held-to-maturity, amortized cost	1,503,973
U.S. Treasury
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	12,106
Securities available-for-sale, Over 1 year through 5 years, fair value	18,179
Fair Value	30,285	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	278,906
Securities available-for-sale, Over 1 year through 5 years, fair value	595,726
Securities available-for-sale, Over 5 years through 10 years, fair value	105,393
Fair Value	980,025	2,349,202
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	31,794
Securities held-to-maturity, Over 10 years, amortized cost	77,768
Total of debt securities held-to-maturity, amortized cost	109,562
Federal agency - MBS
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	398
Securities available-for-sale, Over 1 year through 5 years, fair value	168,346
Securities available-for-sale, Over 5 years through 10 years, fair value	269,438
Fair Value	438,182	693,032
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	315,529
Total of debt securities held-to-maturity, amortized cost	315,529
CMOs - Federal agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	112,918
Securities available-for-sale, Over 1 year through 5 years, fair value	3,606,494
Securities available-for-sale, Over 5 years through 10 years, fair value	1,009,201
Fair Value	4,728,613	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	145,489
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	652,226
Total of debt securities held-to-maturity, amortized cost	797,715
CMOs - Non-agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	4,203
Securities available-for-sale, Over 1 year through 5 years, fair value	14,636
Securities available-for-sale, Over 5 years through 10 years, fair value	26,488
Fair Value	45,327	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	40,790
Securities available-for-sale, Over 1 year through 5 years, fair value	338,418
Securities available-for-sale, Over 5 years through 10 years, fair value	62,250
Securities available-for-sale, Over 10 years, fair value	25,302
Fair Value	466,760	454,474
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	7,460
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	119,559
Securities held-to-maturity, Over 10 years, amortized cost	154,148
Total of debt securities held-to-maturity, amortized cost	281,167
Other debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	12,862
Securities available-for-sale, Over 1 year through 5 years, fair value	292,484
Securities available-for-sale, Over 5 years through 10 years, fair value	44,898
Fair Value	$ 350,244	$ 307,417