Notes Payable (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Debt Instrument [Line Items]
Others	$ 25,082	$ 25,331	$ 25,551
Notes Payable	3,423,286	4,170,183	8,238,277
Fixed Rate 0.66 to 4.95 Percent Advances Due 2011 to 2021
Debt Instrument [Line Items]
-with maturities ranging from 2011 through 2021 paying interest at monthly fixed rates ranging from 0.66% to 4.95% (June 30, 2010 - 1.48% to 5.10%)	704,500	385,000	1,032,873
Fixed Rate 5.10 Percent Advances Due 2010
Debt Instrument [Line Items]
-maturing in 2010 paying interest quarterly at a fixed rate of 5.10%			20,000
Federal Deposit Insurance Corporation | Fixed Rate 2.50 Percent Notes Due April 2015
Debt Instrument [Line Items]
Notes Payable	1,517,843	2,492,928	5,728,954
Fixed Rate 5.25 to 7.86 Percent Term Notes Due 2012 to 2016
Debt Instrument [Line Items]
Notes Payable	278,255	381,133	380,995
Floating Rate 3.00 Percent Term Notes Due 2011 to 2013
Debt Instrument [Line Items]
Notes Payable	801	1,010	1,217
Floating Rate 9.75 Percent Term Notes Due 2011
Debt Instrument [Line Items]
Notes Payable, current			175,000
Fixed Rate 6.125 to 8.327 Percent Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034
Debt Instrument [Line Items]
Junior subordinated deferrable interest debentures (related to trust preferred securities)	439,800	439,800	439,800
Fixed Rate 5.00 Percent Until December 2013 And 9.00 Percent Thereafter Junior Subordinated Deferrable Interest Debentures with no Stated Maturity
Debt Instrument [Line Items]
Junior subordinated deferrable interest debentures (related to trust preferred securities)	$ 457,005	$ 444,981	$ 433,887