Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Billions |
3 Months Ended | 6 Months Ended | 12 Months Ended | ||||
|---|---|---|---|---|---|---|---|
Feb. 22, 2018 |
Feb. 21, 2018 |
Apr. 30, 2018 |
Apr. 30, 2017 |
Apr. 30, 2018 |
Apr. 30, 2017 |
Oct. 31, 2017 |
|
| Equity, Class of Treasury Stock [Line Items] | |||||||
| Cash dividends declared per share, quarterly (in dollars per share) | $ 0.1125 | $ 0.075 | $ 0.1125 | $ 0.065 | $ 0.2625 | $ 0.195 | |
| Share Repurchase program | |||||||
| Equity, Class of Treasury Stock [Line Items] | |||||||
| Common stock retired (in shares) | 102.0 | 1.7 | |||||
| Open share repurchases during period (in shares) | 1.4 | ||||||
| Repurchases of common stock recorded as a reduction to stockholders' equity | $ 1.7 | ||||||
| Share repurchase program additional authorized amount | $ 2.5 | ||||||
| Remaining authorized repurchase amount | $ 6.6 | $ 6.6 | |||||