Fair Value Measurements (Details) - USD ($)	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount of liabilities	$ 8,110,000,000	$ 8,107,000,000
Transfers between level 1, level 2, or level 3 of the fair value hierarchy			$ 0
Fair malue, measurements, recurring | Fair value, inputs, level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair values of liabilities	8,800,000,000	8,600,000,000
Fair malue, measurements, recurring | Fair value, inputs, level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in money market funds, time deposits, bankers acceptances and foreign government debentures	$ 3,200,000,000	$ 2,400,000,000