Leases - Supplemental cash flow and other information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 155
Operating cash flows from finance leases	1
Financing cash flows from finance leases	7
Right of use assets obtained in exchange for lease liabilities:
Operating leases	229
Finance leases	$ 54