Current Liabilities - Deferred Services Revenue (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended	9 Months Ended
Sep. 29, 2012	Dec. 31, 2011	Sep. 29, 2012 Service Contracts	Oct. 01, 2011 Service Contracts	Sep. 29, 2012 Service Contracts	Oct. 01, 2011 Service Contracts	Mar. 31, 2012 Service Contracts	Apr. 02, 2011 Service Contracts
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the period					$ 4,991	$ 2,903	$ 5,602	$ 4,717
Additions			1,478	1,374	5,332	6,585
Revenue recognized			(1,153)	(1,362)	(4,396)	(4,759)
Balance, end of the period			5,927	4,729	5,927	4,729	5,602	4,717
Balance sheet classification
Deferred service income-short term	32,300	20,700	4,636	3,360	4,636	3,360
Deferred service income-long term	$ 1,291	$ 1,458	$ 1,291	$ 1,369	$ 1,291	$ 1,369

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Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

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