Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Expected remaining maturities of debt securities available-for-sale, fair value
Fair Value	$ 6,865,881	$ 7,571,901
Total debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	1,041,817
Securities available-for-sale, Over 1 year through 5 years, fair value	5,238,882
Securities available-for-sale, Over 5 years through 10 years, fair value	533,178
Securities available-for-sale, Over 10 years, fair value	50,498
Fair Value	6,864,375	7,570,674
Expected remaining maturities of debt securities available-for-sale, amortized cost
Securities available-for-sale, One year or less, amortized cost	1,035,552
Securities available-for-sale, Over 1 year through 5 years, amortized cost	5,130,739
Securities available-for-sale, Over 5 years through 10 years, amortized cost	506,789
Securities available-for-sale, Over 10 years, amortized cost	50,345
Total of debt securities available-for-sale, amortized cost	6,723,425
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	11,447
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	105,427
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	844,557
Securities held-to-maturity, Over 10 years, amortized cost	138,798
Total of debt securities held-to-maturity, amortized cost	1,100,229
U.S. Treasury
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	5,003
Securities available-for-sale, Over 1 year through 5 years, fair value	12,205
Fair Value	17,208	19,182
Federal agency - Debt
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	663,719
Securities available-for-sale, Over 1 year through 5 years, fair value	335,488
Fair Value	999,207	1,973,862
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	10,947
Securities held-to-maturity, Over 10 years, amortized cost	92,492
Total of debt securities held-to-maturity, amortized cost	103,439
Federal agency - MBS
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	11
Securities available-for-sale, Over 1 year through 5 years, fair value	455,069
Securities available-for-sale, Over 5 years through 10 years, fair value	236,592
Fair Value	691,672	681,044
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	2,663
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	198,100
Total of debt securities held-to-maturity, amortized cost	200,763
CMOs - Federal agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	309,857
Securities available-for-sale, Over 1 year through 5 years, fair value	4,012,348
Securities available-for-sale, Over 5 years through 10 years, fair value	155,059
Fair Value	4,477,264	4,326,907
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	92,378
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	549,724
Total of debt securities held-to-maturity, amortized cost	642,102
CMOs - Non-agency
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	12,442
Securities available-for-sale, Over 1 year through 5 years, fair value	20,992
Securities available-for-sale, Over 5 years through 10 years, fair value	32,032
Fair Value	65,466	69,001
State and municipal
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	47,369
Securities available-for-sale, Over 1 year through 5 years, fair value	218,736
Securities available-for-sale, Over 5 years through 10 years, fair value	67,047
Securities available-for-sale, Over 10 years, fair value	50,498
Fair Value	383,650	401,604
Expected remaining maturities of debt securities held-to-maturity, amortized cost
Securities held-to-maturity, One year or less, amortized cost	500
Securities held-to-maturity, Over 1 year through 5 years, amortized cost	10,386
Securities held-to-maturity, Over 5 years through 10 years, amortized cost	96,733
Securities held-to-maturity, Over 10 years, amortized cost	46,306
Total of debt securities held-to-maturity, amortized cost	153,925
Other debt securities
Expected remaining maturities of debt securities available-for-sale, fair value
Securities available-for-sale, One year or less fair value	3,416
Securities available-for-sale, Over 1 year through 5 years, fair value	184,044
Securities available-for-sale, Over 5 years through 10 years, fair value	42,448
Fair Value	$ 229,908	$ 99,074