Leases (Lease Costs) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 20	$ 58
Short-term lease cost	2	7
Variable lease cost	3	13
Total lease cost	$ 25	$ 78