Reconciliation of Statutory U.S. Federal Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	21.00%
Transition tax			(0.20%)
State	2.30%	2.30%	2.20%
Research and development tax credit	(1.40%)	(0.90%)	(0.80%)
Tax on foreign earnings	0.80%	0.90%	1.00%
Other, net	(1.00%)	(0.30%)	(1.30%)
Effective income tax rate	21.70%	23.00%	21.90%