Weighted Average Shares - Calculation of Weighted Average Shares (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Basic weighted-average common shares outstanding	172,333	173,287	170,676
Effect of dilutive stock options	5,073	6,264	3,468
Diluted weighted-average common and common-equivalent shares outstanding	177,406	179,551	174,144