Leases - Lease Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease costs	$ 84
Short-term lease costs	321
Variable lease costs	107
Total lease costs	512
Cash paid for amounts included in the measurement of operating lease liabilities	100
ROU assets obtained in exchange for new operating lease liabilities(d)	293
ROU asset	$ 199