Investments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 28, 2013	Dec. 31, 2012
Amortized Cost And Approximate Fair Value Of Held To Maturity Securities [Abstract]
Amortized cost, Current	$ 0.5	$ 0.6
Amortized cost, Noncurrent	3.0	2.8
Unrealized gains, Noncurrent	0.1	0.1
Fair Value, Current	0.5	0.6
Fair Value, Noncurrent	3.1	2.9
Maturities of held-to-maturity securities
Amortized Cost, Within One Year	0.5
Amortized Cost, One to Five Years	1.6
Amortized Cost, Five to Ten Years	0.2
Amortized Cost, After Ten Years	1.2
Amortized Cost, Total	3.5
Approximate Fair Value, Within One Year	0.5
Approximate Fair Value, One to Five Years	1.7
Approximate Fair Value, Five To Ten Years	0.2
Approximate Fair Value, After Ten Years	1.2
Approximate Fair Value, Total	3.6
Investments Textuals [Abstract]
Fair Value Of Investments In Debt And Marketable Securities Whose Value Is Less Than Historical Cost	$ 1.0	$ 0.8
Percentage Of Investments Having Value Less Than Historical Cost	0.27	0.22