Earnings per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 01, 2012	Jul. 03, 2011	Jul. 01, 2012	Jul. 03, 2011	May 16, 2012
Net Income
Continuing operations	$ 18.5	$ 12.9	$ 34.2	$ 24.0
Income from discontinued operations, net of taxes		1.7		1.7
Net income	18.5	14.6	34.2	25.7
Shares
Shares	36.5	37.6	36.7	37.6
Per Share Amount
Continuing operations (in dollars per share)	$ 0.51	$ 0.34	$ 0.93	$ 0.64
Discontinued operations (in dollars per share)		$ 0.05		$ 0.05
Net income (in dollars per share)	$ 0.51	$ 0.39	$ 0.93	$ 0.69
Dilutive securities, principally common stock options
Shares	0.1	0.2	0.1	0.1
Net Income
Continuing operations	18.5	12.9	34.2	24.0
Income from discontinued operations, net of taxes		1.7		1.7
Net income	18.5	14.6	34.2	25.7
Weighted average number of shares:
Weighted average number of shares	36.6	37.8	36.8	37.7
Per Share Amount
Continuing operations (in dollars per share)	$ 0.51	$ 0.34	$ 0.93	$ 0.64
Discontinued operations (in dollars per share)		$ 0.05		$ 0.05
Net income (in dollars per share)	$ 0.51	$ 0.39	$ 0.93	$ 0.68
Securities not included in the computation of diluted EPS
Options to purchase shares of Class A Common Stock	0.4	0.3	0.4	0.3
Number of shares of entity's Class A Common Stock authorized to be repurchased					2
Number of shares of Class A common stock repurchased	1.9
Cost of shares of Class A common stock repurchased	$ 63.2