Leases - Components of Lease Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Finance lease cost:
Amortization of right-of-use assets	$ 86
Interest on lease liabilities	24
Operating lease cost	332
Short-term lease cost	75
Variable lease cost	14
Sublease income	(13)
Total lease costs, net	$ 518