Leases - Components of operating lease costs (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lease Cost [Abstract]
Operating lease cost	$ 355	$ 1,083
Short-term lease cost	39	118
Variable lease cost	63	202
Sublease income	(6)	(18)
Total lease cost	$ 451	$ 1,385