Short-Term Borrowings (Summary Of Short-Term Borrowings) (Detail) (USD $)	Jun. 30, 2012 Month		Dec. 31, 2011 Month
Short-term Debt [Line Items]
FHLB advances	$ 335,000,000		$ 156,000,000
Unused overnight federal funds availability	345,000,000	[1]	200,000,000	[1]
Borrowing capacity through the FRB's discount window primary credit program	893,866,000	[2]	1,074,687,000	[2]
Unused FHLB advances availability	276,345,000		261,490,000
Weighted average remaining maturity of FHLB advances at period end (in months)	0.5		1.8
FHLB advances	0.24%		0.33%
FHLB borrowing capacity	$ 576,700,000

[1] Our total availability of overnight fed fund borrowings is not a committed line of credit and is dependent upon lender availability.

[2] Includes federal term auction facilities. Our borrowing capacity changes each quarter subject to available collateral and FRB discount factors.