Investments (Investments In Marketable Securities With Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	Dec. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	$ 136.5	$ 507.3
Unrealized Loss Less than 12 months	(0.9)	(3.1)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months
Fair Value	136.5	507.3
Total Unrealized Loss	(0.9)	(3.1)
Mortgage Backed Debt Obligations Guaranteed By GNMA [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	31.4	115.7
Unrealized Loss Less than 12 months	(0.1)	(1.2)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months
Fair Value	31.4	115.7
Total Unrealized Loss	(0.1)	(1.2)
U.S. Government Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value		218.6
Unrealized Loss Less than 12 months		(0.7)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months
Fair Value		218.6
Total Unrealized Loss		(0.7)
Corporate Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	81.0	47.5
Unrealized Loss Less than 12 months	(0.7)	(0.2)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months
Fair Value	81.0	47.5
Total Unrealized Loss	(0.7)	(0.2)
Foreign Government Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value		92.9
Unrealized Loss Less than 12 months		(0.9)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months
Fair Value		92.9
Total Unrealized Loss		(0.9)
Foreign Government Debt Obligations Guaranteed By Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Loss Less than 12 months, Fair Value	24.1	32.6
Unrealized Loss Less than 12 months	(0.1)	(0.1)
Unrealized Loss Greater than 12 months, Fair Value
Unrealized Loss Greater than 12 months
Fair Value	24.1	32.6
Total Unrealized Loss	$ (0.1)	$ (0.1)