Debt Senior Unsecured Notes (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2020 |
Jun. 30, 2019 |
Dec. 31, 2019 |
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| Debt Instrument [Line Items] | ||||||||||||
| Long-term debt | $ 10,901 | $ 10,901 | $ 11,857 | |||||||||
| Repayments of unsecured debt | 623 | $ 44 | ||||||||||
| 2023 Senior Unsecured Notes | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Long-term debt | [1] | 0 | 0 | 623 | ||||||||
| Repayments of unsecured debt | 623 | |||||||||||
| 2024 Senior Unsecured Notes(2) | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Long-term debt | [2] | 479 | 479 | 479 | ||||||||
| 2025 Senior Unsecured Notes(2) | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Long-term debt | [2] | 1,175 | 1,175 | 1,174 | ||||||||
| 2028 Senior Unsecured Notes | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Long-term debt | [1] | 1,388 | 1,388 | 1,387 | ||||||||
| Senior Unsecured Notes | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Long-term debt | 3,042 | 3,042 | $ 3,663 | |||||||||
| 2022 First Lien Notes | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Early Repayment of Senior Debt | [3] | 245 | ||||||||||
| Long-term debt | [3] | 0 | 0 | |||||||||
| 2024 First Lien Notes | ||||||||||||
| Debt Instrument [Line Items] | ||||||||||||
| Early Repayment of Senior Debt | [4] | 184 | ||||||||||
| Long-term debt | [4] | $ 0 | $ 0 | |||||||||
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