v3.21.1
Revenues (Changes) (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Significant changes to contract liabilities    
Total contract liabilities, at beginning of period $ 456 $ 529
Decrease due to recognition of revenues for goods and services (44) (41)
Increase due to goods and services transferred over time 7 46
Total contract liabilities, at end of period $ 419 $ 534