Fair Value Measurements 1 (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Mar. 31, 2011
Assets:
Interest rate derivatives	$ 27	$ 15
Fair Value, Measurements, Recurring [Member]
Assets:
Foreign exchange derivatives	2	7
Interest rate derivatives	27	15
Total Assets	1,403	2,210
Liabilities:
Foreign exchange derivatives	4	1
Total Liabilities	4	1
Fair Value, Measurements, Recurring [Member] | Money markets funds [Member]
Assets:
Investments	1,374	2,009
Fair Value, Measurements, Recurring [Member] | Marketable securities [Member]
Assets:
Investments	0	179
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Foreign exchange derivatives	0	0
Interest rate derivatives	0	0
Total Assets	1,374	2,009
Liabilities:
Foreign exchange derivatives	0	0
Total Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money markets funds [Member]
Assets:
Investments	1,374	2,009
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable securities [Member]
Assets:
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Foreign exchange derivatives	2	7
Interest rate derivatives	27	15
Total Assets	29	201
Liabilities:
Foreign exchange derivatives	4	1
Total Liabilities	4	1
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Money markets funds [Member]
Assets:
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Marketable securities [Member]
Assets:
Investments	$ 0	$ 179