Earnings per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding - basic	144.5	143.7	144.4	143.3
Dilutive effect of stock warrants		0.2	0.0	0.2
Dilutive effect of employee stock plans	2.0	1.5	1.9	1.7
Dilutive potential common shares	2.0	1.7	1.9	1.9
Weighted average shares outstanding - diluted	146.5	145.4	146.3	145.2