Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 46.3	$ 41.5
Denominator:
Denominator for basic earnings per share — weighted average shares	34.9	36.5
Effect of dilutive securities:
Equity compensation plans	0.5	0.6
Denominator for diluted earnings per share — adjusted weighted average and assumed conversion	35.4	37.1
Basic earnings per share (in dollars per share)	$ 1.33	$ 1.14
Diluted earnings per share (in dollars per share)	$ 1.31	$ 1.12