Weighted Average Shares - Calculation of Weighted Average Shares (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Basic weighted-average common shares outstanding	173,489	171,194	172,333
Effect of dilutive stock options	3,103	4,075	5,073
Diluted weighted-average common and common-equivalent shares outstanding	176,592	175,269	177,406