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Assumptions Used in Black-Scholes Model to Determine Fair Value for Stock Option Awards Granted (Detail)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Expected volatility 28.00% 27.00% 27.00%
Risk free Interest rate 2.00% 2.00% 1.00%
Expected life (years) 3 years 6 months 3 years 4 months 24 days 3 years 4 months 24 days
Forfeiture rate 8.00% 9.00% 13.00%
Dividend yield 0.50% 0.30% 0.30%