Investments in Marketable Securities with Unrealized Losses (Detail) (USD $) In Millions, unless otherwise specified	Sep. 28, 2012	Dec. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	$ 67.8	$ 136.5
Unrealized Loss Less than 12 months, Unrealized Loss	(0.7)	(0.9)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	67.8	136.5
Total, Unrealized Loss	(0.7)	(0.9)
Corporate debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	16.2	81.0
Unrealized Loss Less than 12 months, Unrealized Loss	(0.1)	(0.7)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	16.2	81.0
Total, Unrealized Loss	(0.1)	(0.7)
Mortgaged backed debt obligations guaranteed by GNMA
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	29.4	31.4
Unrealized Loss Less than 12 months, Unrealized Loss	(0.3)	(0.1)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	29.4	31.4
Total, Unrealized Loss	(0.3)	(0.1)
Foreign government debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	22.2
Unrealized Loss Less than 12 months, Unrealized Loss	(0.3)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	22.2
Total, Unrealized Loss	(0.3)
Foreign corporate debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value		24.1
Unrealized Loss Less than 12 months, Unrealized Loss		(0.1)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value		24.1
Total, Unrealized Loss		$ (0.1)