Stock-Based Compensation Schedule of Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions |
3 Months Ended | 6 Months Ended | 29 Months Ended | ||
|---|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
|
| May 2014 Repurchase Program [Member] [Member] | |||||
| Equity, Class of Treasury Stock [Line Items] | |||||
| Stock Repurchased and Retired During Period, Value | $ 0 | $ 0 | $ 0 | $ 57 | $ 394 |
| Stock Repurchased and Retired During Period, Shares | 0.0 | 0.0 | 0.0 | 1.0 | 9.2 |
| May 2015 Repurchase Program [Member] [Member] | |||||
| Equity, Class of Treasury Stock [Line Items] | |||||
| Stock Repurchased and Retired During Period, Value | $ 127 | $ 126 | $ 256 | $ 201 | |
| Stock Repurchased and Retired During Period, Shares | 1.6 | 1.8 | 3.5 | 3.0 | |
| Repurchase Program, Total | |||||
| Equity, Class of Treasury Stock [Line Items] | |||||
| Stock Repurchased and Retired During Period, Value | $ 127 | $ 126 | $ 256 | $ 258 | |
| Stock Repurchased and Retired During Period, Shares | 1.6 | 1.8 | 3.5 | 4.0 | |