Unearned Revenue and Performance Obligations (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Apr. 30, 2017 |
Apr. 30, 2016 |
|
| Deferred Revenue Disclosure [Abstract] | ||
| Subscription revenue recognized that was included in total unearned revenue balance at beginning of period | $ 361 | $ 251 |
| Revenue is expected to be recognized from remaining performance obligations for subscription contracts | $ 4,000 | |
| Remaining performance obligations to be recognized in the next 2 years | 66.67% | |
| Recognition period | 24 months | |