Receivables - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended	12 Months Ended	1 Months Ended
	Mar. 31, 2012	Sep. 30, 2013 Agreement Institution	Dec. 31, 2012	Mar. 31, 2012 Minimum [Member]	May 31, 2013 Maximum [Member]	Mar. 31, 2012 Maximum [Member]
Schedule Of Financial Receivables [Line Items]
Number of arrangement with different financial institution to sell customer receivables		3
Asset servicing value		$ 0
Liability servicing value		0
Funding of customer receivables sold				50		250
Funding of customer receivables sold after amendment					500
Deferred purchase price receivable	254
Additional funding received		105	205
Purchase price receivable		285
Number of additional financial institution		2
Amount of cash draws under arrangement		388
Amount of cash repayments under arrangement		283
Accounts receivables		8,537
Cash collections		$ 7,942