Amortized Cost and Fair Value of Available for Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 28, 2015	Dec. 27, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 103,612	$ 103,306
Gross Unrealized Gains	629	506
Gross Unrealized Losses	113	343
Fair Value	104,128	103,469
Money market investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,060	1,729
Fair Value	1,060	1,729
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,078	5,106
Gross Unrealized Gains	2	1
Gross Unrealized Losses	22	50
Fair Value	5,058	5,057
Corporate bonds and direct obligations of government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	77,823	76,964
Gross Unrealized Gains	614	491
Gross Unrealized Losses	87	284
Fair Value	78,350	77,171
U.S. Treasury Obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,651	19,507
Gross Unrealized Gains	13	14
Gross Unrealized Losses	4	9
Fair Value	$ 19,660	$ 19,512

This item represents the cost of debt 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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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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Amount of debt securities categorized neither as held-to-maturity nor trading.

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