Earnings per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding - basic	123,400,000	144,600,000	126,900,000	144,700,000
Dilutive effect of employee stock plans	900,000	1,600,000	1,000,000.0	1,700,000
Weighted average shares outstanding - diluted	124,300,000	146,200,000	127,900,000	146,400,000