Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 29, 2015	Dec. 28, 2014
Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	398,317	$ 636,743
Long-term marketable securities	183,298	167,820
Debt Securities | US Treasury Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	89,926	238,488
Debt Securities | Corporate Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	183,842	208,346
Long-term marketable securities	74,605	71,191
Debt Securities | US Agency Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	24,013	32,009
Long-term marketable securities	108,693	95,204
Debt Securities | Municipal Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	5,294	13,622
Long-term marketable securities	0	1,425
Debt Securities | Certificates of Deposit
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	85,245	109,293
Debt Securities | Commercial Paper
Schedule of Held-to-maturity Securities [Line Items]
Short-term marketable securities	9,997	$ 34,985
Short-term Marketable Securities | Minimum [Member]
Schedule of Held-to-maturity Securities [Line Items]
Term of investments	1 month
Short-term Marketable Securities | Maximum [Member]
Schedule of Held-to-maturity Securities [Line Items]
Term of investments	12 months
Long-term Marketable Securities [Member] | Minimum [Member]
Schedule of Held-to-maturity Securities [Line Items]
Term of investments	14 months
Long-term Marketable Securities [Member] | Maximum [Member]
Schedule of Held-to-maturity Securities [Line Items]
Term of investments	36 months