Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Amount of unrealized holding loss before gain recognized in the income statement for investments in trading securities.

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Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Investments (Details) - USD ($) $ in Thousands	Oct. 03, 2015	Sep. 27, 2014	Oct. 03, 2015	Sep. 27, 2014	Dec. 31, 2014
Investments
Total short term investments, amortized cost	$ 712,678		$ 712,678		$ 497,230
Total short term investments, fair value	689,443		689,443		490,566
Unrealized losses related to trading securities	22,377	$ 3,774	20,902	$ 3,149
Available-for-sale securities.
Investments
Amortized Cost	100,648		100,648		167,049
Fair Value	100,648		100,648		167,096
Money market funds
Investments
Amortized Cost	100,648		100,648		142,432
Fair Value	100,648		100,648		142,432
Corporate bonds
Investments
Amortized Cost					11,000
Fair Value					11,015
U.S. Government agency securities
Investments
Amortized Cost					9,684
Fair Value					9,666
Other available-for-sale securities
Investments
Amortized Cost					3,933
Fair Value					3,983
Trading securities.
Investments
Amortized Cost	612,030		612,030		330,181
Fair Value	588,795		588,795		323,470
Domestic equity securities
Investments
Amortized Cost	167,770		167,770
Fair Value	158,815		158,815
High yield trading debt securities
Investments
Amortized Cost	125,347		125,347		187,491
Fair Value	122,178		122,178		181,483
Domestic equity mutual fund
Investments
Amortized Cost	86,309		86,309		83,809
Fair Value	80,525		80,525		82,542
Domestic equity ETF
Investments
Amortized Cost	78,925		78,925		31,307
Fair Value	77,443		77,443		32,651
Foreign equity securities
Investments
Amortized Cost	78,876		78,876
Fair Value	76,669		76,669
Money market funds held in trading accounts
Investments
Amortized Cost	40,152		40,152		21,401
Fair Value	40,152		40,152		21,401
Foreign equity mutual fund
Investments
Amortized Cost	20,000		20,000
Fair Value	19,831		19,831
Collateralized loan obligation
Investments
Amortized Cost	10,000		10,000
Fair Value	9,791		9,791
Other trading securities
Investments
Amortized Cost	4,651		4,651		6,173
Fair Value	3,391		3,391		$ 5,393
Denominated in British pounds \| Money market funds
Investments
Fair Value	970		970
Denominated in Canadian dollars \| Money market funds
Investments
Fair Value	$ 147		$ 147