Fair Value Measurements and Other-Than-Temporary Impairments - Investments at Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Sep. 27, 2014	Dec. 28, 2013
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	$ 314,455	$ 296,972
Gross Unrealized Gains	26	31
Gross Unrealized Losses	(177)	(155)
Fair Value	314,304	296,848
Money Market Funds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	15,369	51,749
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	15,369	51,749
Certificates of Deposit [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	3,460	3,840
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	3,460	3,840
Commercial Paper [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	83,838	85,870
Gross Unrealized Gains	2	2
Gross Unrealized Losses	(2)	(12)
Fair Value	83,838	85,860
Corporate Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	202,959	150,711
Gross Unrealized Gains	19	27
Gross Unrealized Losses	(174)	(143)
Fair Value	202,804	150,595
U.S. Treasuries [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	8,829	4,802
Gross Unrealized Gains	5	2
Gross Unrealized Losses	(1)	0
Fair Value	$ 8,833	$ 4,804