Leases - Maturities of Lease Liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Operating Leases
2019	$ 18
2020	38
2021	36
2022	35
2023	32
2024	27
Thereafter	99
Total lease payments	285
Less imputed interest	(58)
Total net present value	227
Finance Leases
2019	11
2020	19
2021	17
2022	15
2023	8
2024	4
Thereafter	12
Total lease payments	86
Less imputed interest	(19)
Total net present value	67
Total
2019	29
2020	57
2021	53
2022	50
2023	40
2024	31
Thereafter	111
Total lease payments	371
Less imputed interest	(77)
Total leased liabilities	294
Sublease receipts	$ 13
Term of sublease income	14 years