Leases Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lease Costs [Abstract]
Operating lease cost	$ 282
Variable lease cost	49
Sublease income	(89)	$ (72)	$ (46)
Net lease cost	$ 242