Fair Value Measurements - Investments at Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 28, 2015	Dec. 27, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	$ 324,725	$ 326,149
Gross Unrealized Gains	31	3
Gross Unrealized Losses	(208)	(447)
Fair Value	324,548us-gaap_AvailableForSaleSecurities	325,705us-gaap_AvailableForSaleSecurities
Money market funds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	39,633	21,478
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	39,633	21,478
Certificates of deposit
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	9,460	8,060
Gross Unrealized Gains	5	0
Gross Unrealized Losses	0	0
Fair Value	9,465	8,060
Commercial paper
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	21,691	46,073
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Fair Value	21,690	46,072
Corporate bonds
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	223,425	235,713
Gross Unrealized Gains	12	2
Gross Unrealized Losses	(199)	(430)
Fair Value	223,238	235,285
U.S. agency notes
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	14,507
Gross Unrealized Gains	5
Gross Unrealized Losses	(4)
Fair Value	14,508
U.S. treasuries
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Adjusted Amortized Cost	16,009	14,825
Gross Unrealized Gains	9	1
Gross Unrealized Losses	(4)	(16)
Fair Value	$ 16,014	$ 14,810

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

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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