Additional Information (Schedule of Rental Commitments and Sublease Income Under Non-Cancelable Operating Leases) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Rental Commitments
2018	$ 38
2019	33
2020	28
2021	26
2022	23
Thereafter	44
Total	192
Sublease Income
2018	5
2019	5
2020	5
2021	5
2022	5
Thereafter	5
Total	$ 30