Leases - Summary of Amounts Relevant to Company's Assets Leased for Use in its Operations (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 75
Operating cash flows from finance leases	2
Financing cash flows from finance leases	3
Right of use assets obtained in exchange for new operating lease liabilities	36
Right of use assets obtained in exchange for new finance lease liabilities	$ 1
Weighted-average remaining lease term of operating leases (in years)	7 years 9 months 18 days
Weighted-average remaining lease term of finance leases (in years)	10 years 8 months 12 days
Weighted-average discount rate of operating leases	3.30%
Weighted-average discount rate of finance leases	17.30%