Leases - Lease Costs (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Abstract]
Operating lease costs	$ 21	$ 61
Short-term lease costs	94	251
Variable lease costs	24	96
Total lease costs	139	408
Cash paid for amounts included in the measurement of operating lease liabilities		71
ROU assets obtained in exchange for new operating lease liabilities(d)		296
ROU asset	$ 226	$ 226