Leases - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 353	$ 361
Operating cash flows from finance leases	1	1
Financing cash flows from finance leases	1	1
Right-of-use assets obtained in exchange for new lease liabilities:
Operating leases	$ 193	$ 217