Net Income Per Share (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income, as reported, for basic net income per share	$ 95.6	$ 127.1	$ 112.3
Weighted average common shares outstanding (in shares)	72,000,000	70,900,000	69,600,000
Assumed stock options exercised and awards vested, based on the treasury stock method (in shares)	1,800,000	1,900,000	1,700,000
Assumed conversion of convertible debt, based on the if-converted method (in shares)	0	0	100,000
Weighted average shares assuming dilution (in shares)	73,800,000	72,800,000	71,400,000
Antidilutive options excluded from computation of diluted net income per share (in shares)	700,000	500,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	700,000