Leases - Components of Lease Costs (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 414
Finance lease cost:
Amortization of leased assets	43
Interest on lease obligations	21
Short-term lease cost	164
Variable lease cost	89
Sublease income	(12)
Total lease cost	$ 719