Contingencies (Federal Government's Lawsuit) (Details) - USD ($) $ in Millions |
1 Months Ended | 3 Months Ended | 72 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
Aug. 31, 2006 |
Dec. 31, 2020 |
Sep. 30, 2020 |
Jun. 30, 2020 |
Mar. 31, 2020 |
Dec. 31, 2019 |
Sep. 30, 2019 |
Jun. 30, 2019 |
Mar. 31, 2019 |
Dec. 31, 2019 |
|
| Loss Contingencies [Line Items] | ||||||||||
| Provision related to litigation recorded | $ 7 | $ 34 | $ 18 | $ 24 | $ 29 | $ 3 | $ 28 | $ 17 | ||
| Federal Governments Lawsuit [Member] | ||||||||||
| Loss Contingencies [Line Items] | ||||||||||
| Disclosure period | 10 years | |||||||||
| Implementation of Corrective Communications [Member] | Federal Governments Lawsuit [Member] | ||||||||||
| Loss Contingencies [Line Items] | ||||||||||
| Provision related to litigation recorded | $ 36 | |||||||||