Fair Value Measurements (Details) - USD ($) |
Dec. 31, 2019 |
Mar. 31, 2019 |
---|---|---|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Carrying amount of liabilities | $ 7,700,000,000 | $ 7,600,000,000 |
Recurring | Fair value, inputs, level 2 | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Carrying amount of liabilities | 7,700,000,000 | 7,600,000,000 |
Estimated fair values of liabilities | 8,200,000,000 | 7,900,000,000 |
Recurring | Fair value, inputs, level 1 | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Investments in money market funds | 676,000,000 | 1,200,000,000 |
Nonrecurring | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Liabilities measured at fair value | $ 0 | $ 0 |