Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	$ 1,567
Fair value of liabilities measured on a recurring basis	13
Short-term Investments | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	338
Short-term Investments | Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	322
Other Assets | Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	841
Other Assets | Cross Currency Swap and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	66
Other Liabilities | Cross Currency Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities measured on a recurring basis	13
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	338	[1]
Level 1 | Short-term Investments | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	338	[1]
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	1,229	[2]
Fair value of liabilities measured on a recurring basis	13	[2]
Level 2 | Short-term Investments | Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	322	[2]
Level 2 | Other Assets | Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	841	[2]
Level 2 | Other Assets | Cross Currency Swap and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments measured on a recurring basis	66	[2]
Level 2 | Other Liabilities | Cross Currency Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities measured on a recurring basis	$ 13	[2]

[1] quoted prices in active markets for identical assets or liabilities

[2] observable inputs other than quoted prices in active markets for identical assets and liabilities