Goodwill (Details) $ in Thousands	9 Months Ended
	Oct. 01, 2016 USD ($)
Changes in the carrying amount of goodwill
Balance at the beginning of the period, gross	$ 153,387
Effect of foreign currency translation	(1,527)
Balance at the end of the period, gross	151,860
Balance at the beginning of the period, Accumulated impairment losses	(76,417)
Balance at the end of the period, Accumulated impairment losses	(76,417)
Balance at the beginning of the period, net	76,970
Balance at the end of the period, net	$ 75,443