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Capital Structure - Summary of Changes in Shares Repurchased (Details) - USD ($) $ / shares in Units, $ in Millions | 2 Months Ended | 12 Months Ended | 14 Months Ended
--- | --- | --- | ---
Feb. 28, 2019 | Dec. 31, 2018 | Feb. 28, 2019
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) |  | 35,234,664 |
Capital Allocation Plan, Open Market Repurchases |  |  |
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) |  | 11,097,631,000,000 |
Amounts paid for shares purchased (in millions) |  | $ 396 |
Capital Allocation Plan, Accelerated Repurchase Agreement May 2018 |  |  |
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) |  | 10,829,903,000,000 |
Amounts paid for shares purchased (in millions) |  | $ 354 |
Capital Allocation Plan, Accelerated Repurchase Program September 2018 |  |  |
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) |  | 13,307,130,000,000 |
Amounts paid for shares purchased (in millions) |  | $ 500 |
Capital Allocation Plan |  |  |
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) |  | 35,234,664,000,000 |
Amounts paid for shares purchased (in millions) |  | $ 1,250 |
Subsequent Event | Capital Allocation Plan, Open Market Repurchases |  |  |
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) | 6,153,415,000,000 |  |
Amounts paid for shares purchased (in millions) | $ 250 |  |
Subsequent Event | Capital Allocation Plan |  |  |
Capital Allocation Plan [Line Items] |  |  |
Total number of shares purchased (in shares) |  |  | 41,388,079,000,000
Average price paid per share (in shares) |  |  | $ 36.24
Amounts paid for shares purchased (in millions) |  |  | $ 1,500

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