Financial Instruments (Fair Value Of Short-Term Investments By Stated Maturity Date Schedule) (Details) - USD ($)
$ in Millions |
Sep. 30, 2016 |
Mar. 31, 2016 |
| Financial Instruments |
|
|
|
| Short-term investments, Fair Value |
$ 1,520
|
$ 1,341
|
[1] |
| Due in 1 year or less [Member] |
|
|
|
| Financial Instruments |
|
|
|
| Due in 1 year or less, Amortized Cost |
749
|
571
|
|
| Due in 1 year or less, Fair Value |
749
|
571
|
|
| Due in 1-2 years [Member] |
|
|
|
| Financial Instruments |
|
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis |
415
|
461
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value |
416
|
462
|
|
| Due in 2-3 years [Member] |
|
|
|
| Financial Instruments |
|
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis |
295
|
295
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value |
296
|
296
|
|
| Due in 3-4 years [Member] |
|
|
|
| Financial Instruments |
|
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis |
59
|
12
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value |
$ 59
|
$ 12
|
|
|
|