Accounting Policies (Details 6) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended								12 Months Ended
	May 16, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 02, 2011
Net Income
Net income		$ 15.5	$ 18.7	$ 18.5	$ 15.7	$ 17.0	$ 23.7	$ 14.6	$ 11.1	$ 68.4	$ 66.4	$ 58.8
Shares
Weighted average number of shares (in shares)										36.0	37.3	37.3
Per Share Amount
Per Share Amount (in dollars per share)		$ 0.44	$ 0.53	$ 0.51	$ 0.42	$ 0.47	$ 0.63	$ 0.39	$ 0.30	$ 1.90	$ 1.78	$ 1.58
Dilutive securities, principally common stock options
Shares										0.1	0.2	0.1
Dilutive securities, principally common stock options
Per share amount (in dollars per share)												$ (0.1)
Net Income
Net income										68.4	66.4	58.8
Weighted average number of shares:
Weighted average number of shares										36.1	37.5	37.4
Per Share Amount
NET INCOME (in dollars per share)		$ 0.44	$ 0.53	$ 0.51	$ 0.42	$ 0.47	$ 0.63	$ 0.39	$ 0.29	$ 1.90	$ 1.78	$ 1.57
Securities not included in the computation of diluted EPS
Options to purchase shares of Class A Common Stock										0.2	0.7	0.5
Number of shares of entity's Class A Common Stock authorized to be repurchased	2												1
Number of shares of Class A common stock repurchased	2.0						1.0
Cost of shares of Class A common stock repurchased	65.8						27.2
Shipping and Handling
Shipping and handling costs included in selling, general and administrative expense										38.0	38.1	33.5
Research and Development
Research and development costs included in selling, general, and administrative expense										$ 20.7	$ 20.9	$ 18.6