Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Weighted average common shares outstanding for basic computations (in shares)	280,000,000.0	282,000,000.0	284,500,000
Weighted average dilutive effect of equity awards (in shares)	1,200,000	1,800,000	2,300,000
Weighted average common shares outstanding for diluted computations (in shares)	281,200,000	283,800,000	286,800,000
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0	0