Leases - Schedule of Components of Lease Expense (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Operating leases:
Operating lease expense	$ 110	$ 317
Finance leases:
Amortization of leased assets	78	210
Interest on lease liabilities	27	78
Total finance lease expense	105	288
Total lease expense	$ 215	$ 605