Leases - Schedule of Maturities of Lease Obligations (Detail) $ in Millions	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating Leases, 2019	$ 308
Operating Leases, 2020	183
Operating Leases, 2021	71
Operating Leases, 2022	64
Operating Leases, 2023	64
Operating Leases, Remaining years	197
Total lease payments	887
Less: Imputed interest	(85)
Total lease obligations	802
Financing Leases, 2019	48
Financing Leases, 2020	36
Financing Leases, 2021	36
Financing Leases, 2022	36
Financing Leases, 2023	36
Financing Leases, Remaining years	248
Total lease payments	440
Less: Imputed interest	(154)
Total lease obligations	$ 286