Investments in Marketable Securities with Unrealized Losses (Detail) (USD $) In Millions, unless otherwise specified	Jun. 29, 2012	Dec. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	$ 211.3	$ 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	211.3	136.5
Total, Unrealized Loss	(0.7)	(0.9)
U.S. government debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	46.2
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	46.2
Total, Unrealized Loss	(0.1)
Corporate debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	46.3	81.0
Unrealized Loss Less than 12 months, Unrealized Loss	(0.2)	(0.7)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	46.3	81.0
Total, Unrealized Loss	(0.2)	(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	37.1	31.4
Unrealized Loss Less than 12 months, Unrealized Loss	(0.2)	(0.1)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	37.1	31.4
Total, Unrealized Loss	(0.2)	(0.1)
Foreign government debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	49.1
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	49.1
Total, Unrealized Loss	(0.1)
Foreign corporate debt obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	32.6	24.1
Unrealized Loss Less than 12 months, Unrealized Loss	(0.1)	(0.1)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months, Unrealized Loss
Total, Fair Value	32.6	24.1
Total, Unrealized Loss	$ (0.1)	$ (0.1)