Investments and Fair Value Measurements-Fin Assets and Liabilities 1 (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 30, 2012
Financial assets measured at fair value on a recurring basis
Total financial assets	$ 5,995,327	$ 5,548,126
Financial Liabilities measured at fair value on a recurring basis
Total financial liabilities	34,821	13,584
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets measured at fair value on a recurring basis
Total financial assets	860,953	610,129
Financial Liabilities measured at fair value on a recurring basis
Total financial liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Financial assets measured at fair value on a recurring basis
Total financial assets	5,134,374	4,937,997
Financial Liabilities measured at fair value on a recurring basis
Total financial liabilities	34,821	13,584
Significant Unobservable Inputs (Level 3) [Member]
Financial assets measured at fair value on a recurring basis
Total financial assets	0	0
Financial Liabilities measured at fair value on a recurring basis
Total financial liabilities	0	0
Derivative Liabilities [Member]
Financial Liabilities measured at fair value on a recurring basis
Derivative liabilities	34,821	13,584
Derivative Liabilities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Liabilities measured at fair value on a recurring basis
Derivative liabilities	0	0
Derivative Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial Liabilities measured at fair value on a recurring basis
Derivative liabilities	34,821	13,584
Derivative Liabilities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial Liabilities measured at fair value on a recurring basis
Derivative liabilities	0	0
Money Market Funds [Member]
Financial assets measured at fair value on a recurring basis
Money market funds	795,213	582,743
Money Market Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets measured at fair value on a recurring basis
Money market funds	795,213	582,743
Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets measured at fair value on a recurring basis
Money market funds	0	0
Money Market Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets measured at fair value on a recurring basis
Money market funds	0	0
Fixed Income Securities [Member]
Financial assets measured at fair value on a recurring basis
Fixed income securities	5,185,177	4,945,325
Fixed Income Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets measured at fair value on a recurring basis
Fixed income securities	65,740	27,386
Fixed Income Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets measured at fair value on a recurring basis
Fixed income securities	5,119,437	4,917,939
Fixed Income Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets measured at fair value on a recurring basis
Fixed income securities	0	0
Derivative Assets [Member]
Financial assets measured at fair value on a recurring basis
Derivative assets	14,937	20,058
Derivative Assets [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets measured at fair value on a recurring basis
Derivative assets	14,937	20,058
Derivative Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets measured at fair value on a recurring basis
Derivative assets	$ 0	$ 0