Income Taxes - Reconciliation of United States Federal Statutory Tax Rate to Effective Tax Rate on Income Before Provision for Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. statutory tax rate	21.00%	21.00%	21.00%
State and local taxes, net of federal tax benefit	2.30%	2.20%	2.20%
Benefit of foreign operations	(1.50%)	(0.10%)	1.80%
U.S. Tax Act Impact	0	0	(0.028)
Other	(1.50%)	(2.10%)	(1.10%)
Effective tax rate	20.30%	21.00%	21.10%
Income tax paid	$ 514	$ 458	$ 442