Leases - Operating Lease Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 222
Amortization of right-of-use assets	29
Interest on lease liabilities	4
Short-term lease cost	39
Variable lease cost	474
Sublease income	(6)
Total lease cost	$ 762