Equity - Weighted Average Assumptions Used in Valuation (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Volatility	31.90%	31.60%	28.70%
Risk-free interest rate	1.40%	2.50%	2.40%
Dividend yield	0.60%	0.80%	0.90%
Expected life (years)	4 years 3 months 18 days	4 years 1 month 6 days	3 years 10 months 24 days
Weighted average fair value per option	$ 14.83	$ 8.89	$ 7.35