Leases - Summary of Amounts Relevant to Company's Assets Leased for Use in its Operations (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 76	$ 151
Operating cash flows from finance leases	2	4
Financing cash flows from finance leases	2	5
Right of use assets obtained in exchange for new operating lease liabilities	37	73
Right of use assets obtained in exchange for new finance lease liabilities	$ 1	$ 2