Earnings per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding - basic	121,400,000	142,500,000	125,100,000	143,900,000
Dilutive effect of employee stock plans	800,000	1,400,000	900,000	1,700,000
Weighted average shares outstanding - diluted	122,200,000	143,900,000	125,900,000	145,600,000