Debt Obligations (1.75% Senior Unsecured Notes Due 2023) (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
May 31, 2016 |
|
| Debt Instrument [Line Items] | ||
| Increase (decrease) in carrying amount | $ (1,262) | |
| 1.75% senior unsecured notes due May 19, 2023 | ||
| Debt Instrument [Line Items] | ||
| Stated rate | 1.75% | |
| Senior Notes | 1.75% senior unsecured notes due May 19, 2023 | ||
| Debt Instrument [Line Items] | ||
| Stated rate | 1.75% | 1.75% |
| Increase (decrease) in carrying amount | $ 62 | |
| Senior Notes | 1.75% senior unsecured notes due May 19, 2023 | Maximum | ||
| Debt Instrument [Line Items] | ||
| Maximum interest rate on debt instrument | 3.75% |