Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee Disclosure [Abstract]
Cash paid for operating leases	$ 306	$ 283
Right-of-use assets obtained in exchange for operating lease liabilities	$ 328	$ 360
Weighted average remaining lease term in years	4 years	4 years
Weighted average discount rate	2.60%	3.20%
Operating lease, cost	$ 304	$ 280
Variable lease costs not included in the lease liability	57	55
Total lease cost	$ 360	$ 335
Rent and other lease-related expenses			$ 305