Fair Value Measurements 1 (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Mar. 31, 2012
Assets:
Interest rate derivatives	$ 22		$ 27
Fair Value, Measurements, Recurring [Member]
Assets:
Foreign exchange derivatives	4	[1]	2	[1]
Interest rate derivatives	22	[1]	27	[1]
Total Assets	1,266		1,403
Liabilities:
Foreign exchange derivatives	4	[1]	4	[1]
Total Liabilities	4		4
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Assets:
Money market funds	1,240	[2]	1,374	[3]
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Total Assets	1,240		1,374
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]
Assets:
Money market funds	1,240		1,374
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Foreign exchange derivatives	4	[1]	2	[1]
Interest rate derivatives	22	[1]	27	[1]
Total Assets	26		29
Liabilities:
Foreign exchange derivatives	4	[1]	4	[1]
Total Liabilities	$ 4		$ 4

[1] See Note H, “Derivatives” for additional information. Interest rate derivatives fair value excludes accrued interest.

[2] At December 31, 2012, the Company had approximately $1,190 million and $50 million of investments in money market funds classified as “Cash and cash equivalents” and “Other noncurrent assets, net” for restricted cash amounts, respectively, in its Condensed Consolidated Balance Sheet.

[3] At March 31, 2012, the Company had approximately $1,324 million and $50 million of investments in money market funds classified as “Cash and cash equivalents” and “Other noncurrent assets, net” for restricted cash amounts, respectively, in its Condensed Consolidated Balance Sheet.