Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income, as reported, for basic net income per share	$ 143.6	$ 95.6	$ 127.1
Weighted average common shares outstanding (in shares)	73,300,000	72,000,000	70,900,000
Assumed stock options exercised and awards vested, based on the treasury stock method (in shares)	1,700,000	1,800,000	1,900,000
Weighted average shares assuming dilution (in shares)	75,000,000	73,800,000	72,800,000
Antidilutive options excluded from computation of diluted net income per share (in shares)	100,000	700,000	500,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	800,000	700,000
Treasury Stock, Shares, Acquired	700,000
Treasury Stock, Value, Acquired, Cost Method	$ 52.2
Treasury Stock Acquired, Average Cost Per Share	$ 74.54