Leases - Supplemental Cash Flow Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 94
Operating cash flows from finance leases	3
Financing cash flows from finance leases	17
Right-of-use assets obtained in exchange for lease liabilities
Operating leases	459
Finance leases	$ 288