Effects on net income of amounts reclassified from accumulated other comprehensive income (loss) (Details) - USD ($)
$ in Millions |
3 Months Ended |
6 Months Ended |
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
| Accumulated Other Comprehensive Income (Loss) [Line Items] |
|
|
|
|
| Amounts reclassified from accumulated other comprehensive income (loss) |
$ (5)
|
$ (5)
|
$ (11)
|
$ (8)
|
| Unrealized Gains (Losses) on Available-for-Sale Securities [Member] |
|
|
|
|
| Accumulated Other Comprehensive Income (Loss) [Line Items] |
|
|
|
|
| Amounts reclassified from accumulated other comprehensive income (loss) |
(1)
|
(1)
|
(1)
|
(1)
|
| Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Interest Income [Member] |
|
|
|
|
| Accumulated Other Comprehensive Income (Loss) [Line Items] |
|
|
|
|
| Amounts reclassified from accumulated other comprehensive income (loss) |
(1)
|
(1)
|
(1)
|
(1)
|
| Unrealized Gains (Losses) on Derivative Instruments [Member] |
|
|
|
|
| Accumulated Other Comprehensive Income (Loss) [Line Items] |
|
|
|
|
| Amounts reclassified from accumulated other comprehensive income (loss) |
(4)
|
(4)
|
(10)
|
(7)
|
| Unrealized Gains (Losses) on Derivative Instruments [Member] | Sales Revenue, Net |
|
|
|
|
| Accumulated Other Comprehensive Income (Loss) [Line Items] |
|
|
|
|
| Amounts reclassified from accumulated other comprehensive income (loss) |
(4)
|
(6)
|
(9)
|
(14)
|
| Unrealized Gains (Losses) on Derivative Instruments [Member] | Research And Development [Member] |
|
|
|
|
| Accumulated Other Comprehensive Income (Loss) [Line Items] |
|
|
|
|
| Amounts reclassified from accumulated other comprehensive income (loss) |
$ 0
|
$ 2
|
$ (1)
|
$ 7
|