Balance Sheet Components - Marketable Securities (Details) - USD ($)	12 Months Ended
Dec. 26, 2015	Dec. 27, 2014
Available-for-sale Securities [Abstract]
Amortized Cost	$ 41,380,000	$ 49,888,000
Available-for-sale Securities, Gross Unrealized Gains	1,000	13,000
Available-for-sale Securities, Gross Unrealized Losses	(56,000)	(4,000)
Available-for-sale Securities Fair Value	$ 41,325,000	49,897,000
Maximum Remaining Maturity of Foreign Currency Derivatives	3 years
Continuous Unrealized Loss Position, 12 Months or More, Fair Value	$ 0	0
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Due in one year or less - Amortized Cost	33,882,000	38,499,000
Due in one year to five years - Amortized Cost	7,498,000	11,389,000
Amortized Cost	41,380,000	49,888,000
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Due in one year or less - Fair Value	33,871,000	38,509,000
Due in one year to five years - Fair Value	7,454,000	11,388,000
Available-for-sale Securities Fair Value	41,325,000	49,897,000
U.S. Treasuries
Available-for-sale Securities [Abstract]
Amortized Cost	18,896,000	42,386,000
Available-for-sale Securities, Gross Unrealized Gains	1,000	13,000
Available-for-sale Securities, Gross Unrealized Losses	(44,000)	(4,000)
Available-for-sale Securities Fair Value	18,853,000	42,395,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost	18,896,000	42,386,000
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Available-for-sale Securities Fair Value	18,853,000	42,395,000
Agency securities (Federal)
Available-for-sale Securities [Abstract]
Amortized Cost	22,484,000	7,502,000
Available-for-sale Securities, Gross Unrealized Gains	0	0
Available-for-sale Securities, Gross Unrealized Losses	(12,000)	0
Available-for-sale Securities Fair Value	22,472,000	7,502,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost	22,484,000	7,502,000
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Available-for-sale Securities Fair Value	$ 22,472,000	$ 7,502,000

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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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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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Maximum amount of time remaining before foreign currency exchange rate derivatives mature or expire, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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