Segment and geographical information, Revenues from External Customers and Long-Lived Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 26, 2014	Sep. 26, 2014	Jun. 27, 2014	Mar. 28, 2014	Dec. 27, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Dec. 26, 2014	Dec. 27, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 80,110	$ 88,205	$ 93,567	$ 81,652	$ 87,772	$ 94,840	$ 88,258	$ 84,806	$ 343,534	$ 355,676
Property, plant and equipment, net	26,472				27,955				26,472	27,955
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									184,166	182,033
Property, plant and equipment, net	12,514				14,723				12,514	14,723
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									43,913	46,528
Property, plant and equipment, net	11,482				11,614				11,482	11,614
Tunisia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	1,652				0				1,652	0
Asia, Other Than China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									38,224	52,683
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									70,368	66,520
Property, plant and equipment, net	803				538				803	538
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									6,863	7,912
Property, plant and equipment, net	21				35				21	35
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 0				$ 1,045				$ 0	$ 1,045
One Major Customer [Member] | Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration risk, percentage									12.70%	10.80%
Ten Largest Customers [Member] | Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration risk, percentage									54.10%	49.90%