Weighted Average Shares (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Calculation of Weighted Average Shares

Weighted-average shares were calculated as follows (in thousands):

	Year Ended December 31,
	2018	2017	2016
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