Summary of Borrowed Funds (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Debt Outstanding [Line Items]
FHLB advances	$ 8,945,008	$ 9,314,193
Repurchase agreements	4,125,000	4,125,000
Fed funds purchased	100,000
Total wholesale borrowings	13,170,008	13,439,193
Junior subordinated debentures	427,077	426,936
Senior notes		89,984
Preferred stock of subsidiaries	4,300	4,300
Total borrowed funds	$ 13,601,385	$ 13,960,413