Discontinued Operations - Additional Information (Detail) (USD $)			9 Months Ended			3 Months Ended						1 Months Ended		3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2012 Insurance business	Dec. 31, 2012 Insurance business	Dec. 31, 2011 Insurance business	Jun. 30, 2012 Card and Retail Services	Mar. 31, 2012 Card and Retail Services	May 02, 2012 Card and Retail Services	Dec. 31, 2011 Card and Retail Services	Dec. 31, 2011 Card and Retail Services Revolving Credit Facility [Member]	Dec. 31, 2011 Card and Retail Services Line of Credit [Member]	Aug. 31, 2010 Auto Finance	Mar. 31, 2010 Auto Finance	Sep. 30, 2010 Auto Finance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of insurance operation			$ 181,000,000
Lower of amortized cost or fair value less cost to sell adjustment, before tax			119,000,000
Lower of amortized cost or fair value less cost to sell adjustment, after tax			90,000,000
Available-for-sale securities				1,411,000,000	1,851,000,000
Insurance policy and claim reserves				988,000,000	1,049,000,000
Sold business, premium percentage of receivables								8.75%
Proceeds from divestiture of businesses						11,800,000,000							930,000,000
Pre-tax gain						2,200,000,000							5,000,000	43,000,000
Net cash amount after-tax gain						1,400,000,000							3,000,000	28,000,000
Industry review of enhancement services products	59,000,000
Net intangible assets related to account relationships purchased									29,000,000
Gain on sale of intangible assets							79,000,000
Total amounts on secured financings of credit card receivables										650,000,000
Receivables, collateralizing long-term debt	4,900,000,000	5,300,000,000							195,000,000
Credit card receivables									355,000,000
Open consumer lines of credit											105,000,000,000
Outstanding principal balance												2,600,000,000	431,000,000
Aggregate sales price of assets												2,500,000,000
Net cash proceeds from sale of business												$ 2,100,000,000