Revenue Recognition Contract Assets and Liabilities (Details) $ in Millions |
6 Months Ended |
|---|---|
|
Jun. 30, 2018
USD ($)
| |
| Contract assets: | |
| Contract asset, beginning | $ 35 |
| Additions | 13 |
| Transfers to accounts receivable, net | (33) |
| Contract asset, ending | 15 |
| Contract liabilities: | |
| Contract liability, beginning | 25 |
| Additions | 36 |
| Transfers to operating revenues | (34) |
| Contract liability, ending | $ 27 |