Income Taxes (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2018 |
|
| Investments, Owned, Federal Income Tax Note [Line Items] | |||
| U.S. tax reform provisional income tax charge (benefit) | $ 3,100 | ||
| Deferred tax liability as a percentage of indefinitely reinvested earnings | 24.00% | ||
| Minimum | |||
| Investments, Owned, Federal Income Tax Note [Line Items] | |||
| Foreign earnings expected to be indefinitely reinvested | $ 200 | ||
| Maximum | |||
| Investments, Owned, Federal Income Tax Note [Line Items] | |||
| Foreign earnings expected to be indefinitely reinvested | $ 300 | ||
| Forecast | |||
| Investments, Owned, Federal Income Tax Note [Line Items] | |||
| U.S. tax reform provisional income tax charge (benefit) | $ (389) | ||