CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 28, 2014	Mar. 29, 2013
Statement of Partners' Capital [Abstract]
Net income (loss)	$ (5,410)	$ 6,421
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	40	(624)
Gain on investments	7	5
Other comprehensive income (loss) before tax	47	(619)
Income tax benefit related to items of other comprehensive income (loss)	(1)	(3)
Other comprehensive income (loss), net of tax	48	(616)
Comprehensive income (loss)	$ (5,362)	$ 5,805