Commitments and Contingencies - Lease Commitments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Operating Leases
2018	$ 45
2019	38
2020	30
2021	19
2022	12
Thereafter	41
Total minimum lease payments	185
Sublease Income
2018	3
2019	3
2020	1
2021	0
2022	0
Thereafter	$ 0