Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value	$ 9,224,702	$ 7,294,303
Unrealized Losses	25,900	36,177
U.S. Government And Federal Agency Obligations [Member]
Fair Value	364,665	455,537
Government-Sponsored Enterprise Obligations [Member]
Fair Value	315,698	201,895
Unrealized Losses		530
Government-Sponsored Enterprise Obligations [Member] | Less Than 12 Months [Member]
Fair Value		10,850
Unrealized Losses		530
Government-Sponsored Enterprise Obligations [Member] | Total [Member]
Fair Value		10,850
Unrealized Losses		530
State And Municipal Obligations [Member]
Fair Value	1,245,284	1,119,485
Unrealized Losses	11,219	16,643
State And Municipal Obligations [Member] | Less Than 12 Months [Member]
Fair Value	65,962	345,775
Unrealized Losses	712	7,470
State And Municipal Obligations [Member] | 12 Months Or Longer [Member]
Fair Value	110,807	82,269
Unrealized Losses	10,507	9,173
State And Municipal Obligations [Member] | Total [Member]
Fair Value	176,769	428,044
Unrealized Losses	11,219	16,643
Agency Mortgage-Backed Securities [Member]
Fair Value	4,106,059	2,491,199
Unrealized Losses	493	3,440
Agency Mortgage-Backed Securities [Member] | Less Than 12 Months [Member]
Fair Value	72,019	660,326
Unrealized Losses	493	3,440
Agency Mortgage-Backed Securities [Member] | Total [Member]
Fair Value	72,019	660,326
Unrealized Losses	493	3,440
Non-Agency Mortgage-Backed Securities [Member]
Fair Value	316,902	455,790
Unrealized Losses	7,812	14,513
Non-Agency Mortgage-Backed Securities [Member] | Less Than 12 Months [Member]
Fair Value	23,672	15,893
Unrealized Losses	784	36
Non-Agency Mortgage-Backed Securities [Member] | 12 Months Or Longer [Member]
Fair Value	118,972	170,545
Unrealized Losses	7,028	14,477
Non-Agency Mortgage-Backed Securities [Member] | Total [Member]
Fair Value	142,644	186,438
Unrealized Losses	7,812	14,513
Asset-Backed Securities [Member]
Fair Value	2,693,143	2,354,260
Unrealized Losses	6,376	1,051
Asset-Backed Securities [Member] | Less Than 12 Months [Member]
Fair Value	1,236,526	487,822
Unrealized Losses	4,982	1,029
Asset-Backed Securities [Member] | 12 Months Or Longer [Member]
Fair Value	87,224	24,928
Unrealized Losses	1,394	22
Asset-Backed Securities [Member] | Total [Member]
Fair Value	1,323,750	512,750
Unrealized Losses	6,376	1,051
Other Debt Securities [Member]
Fair Value	141,260	176,964
Equity Securities [Member]
Fair Value	41,691	39,173
Total Mortgage And Asset-Backed Securities [Member]
Fair Value	7,116,104	5,301,249
Unrealized Losses	14,681	19,004
Total Mortgage And Asset-Backed Securities [Member] | Less Than 12 Months [Member]
Fair Value	1,332,217	1,164,041
Unrealized Losses	6,259	4,505
Total Mortgage And Asset-Backed Securities [Member] | 12 Months Or Longer [Member]
Fair Value	206,196	195,473
Unrealized Losses	8,422	14,499
Total Mortgage And Asset-Backed Securities [Member] | Total [Member]
Fair Value	1,538,413	1,359,514
Unrealized Losses	14,681	19,004
Total Temporarily Impaired Securities [Member] | Less Than 12 Months [Member]
Fair Value	1,398,179	1,520,666
Unrealized Losses	6,971	12,505
Total Temporarily Impaired Securities [Member] | 12 Months Or Longer [Member]
Fair Value	317,003	277,742
Unrealized Losses	18,929	23,672
Total Temporarily Impaired Securities [Member] | Total [Member]
Fair Value	1,715,182	1,798,408
Unrealized Losses	$ 25,900	$ 36,177