Contingent Liabilities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007	Mar. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Line Items]
Standby letters of credit outstanding						$ 4,500,000,000	$ 4,600,000,000
Minimum securities lending related collateral percentage						100.00%	100.00%
Possible loss in future periods in excess of accrual						126,000,000
Gain on redemption of Visa common stock				167,900,000
Remaining Visa shares held by Northern Trust, original cost basis				0
Visa indemnified litigation benefit (charges) recorded	23,100,000	33,000,000	17,800,000	76,100,000	(150,000,000)
Fair value of contingent consideration						51,400,000	50,100,000
Indemnification Agreement
Commitments and Contingencies Disclosure [Line Items]
Collateralized securities loaned, subject to indemnification						79,300,000,000	69,700,000,000
Credit loss liability						$ 0	$ 0