Investments and Fair Value Measurements-Fin Assets and Liabilities 1 (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jan. 01, 2012
Financial assets measured at fair value on a recurring basis
Total financial assets	$ 5,087,831	$ 5,454,454
Financial Liabilities measured at fair value on a recurring basis
Total financial liabilities	6,759	45,835
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets measured at fair value on a recurring basis
Total financial assets	629,833	1,115,931
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	4,457,998	4,338,523
Financial Liabilities measured at fair value on a recurring basis
Total financial liabilities	6,759	45,835
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	6,759	45,835
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	6,759	45,835
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	606,845	901,500
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	606,845	901,500
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	4,474,048	4,527,360
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	22,988	214,431
Fixed Income Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets measured at fair value on a recurring basis
Fixed income securities	4,451,060	4,312,929
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	6,938	21,093
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	6,938	21,093
Derivative Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets measured at fair value on a recurring basis
Derivative assets	0	0
Other Securities [Member]
Financial assets measured at fair value on a recurring basis
Other	0	4,501
Other Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets measured at fair value on a recurring basis
Other	0	0
Other Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets measured at fair value on a recurring basis
Other	0	4,501
Other Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets measured at fair value on a recurring basis
Other	$ 0	$ 0