Leases - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 196
Operating cash flows from finance leases	1	$ 0	$ 0
Financing cash flows from finance leases	6
Right-of-use assets obtained in exchange for new lease obligations:
Operating leases	99
Finance leases	$ 34