Revision of prior period financial statements and out-of-period adjustments (Details) - Effect of the error correction on consolidated statements of operations and comprehensive (loss) income (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revision of prior period financial statements and out-of-period adjustments (Details) - Effect of the error correction on consolidated statements of operations and comprehensive (loss) income [Line Items]
Net sales	$ 16,020	$ 13,928	$ 16,033	$ 14,642	$ 13,264	$ 14,661	$ 14,465	$ 16,169	$ 60,623	$ 58,559	$ 61,260
Operating (loss) income		(670)	(1,458)	(1,340)	(1,916)	(232)	(1,558)	29	(2,869)	(3,677)	(1,766)
Net loss from continuing operations	(2,528)	(1,438)	(2,197)	(1,725)	(2,600)	(770)	(2,159)	(593)	(7,888)	(6,122)	34,697
Net loss from discontinued operations	(682)	(1,118)	(17,303)	(2,901)	(2,141)	(1,700)	(1,370)	(1,501)	(22,004)	(6,712)	(4,719)
Net (loss) income	(3,210)	(2,556)	(19,500)	(4,626)	(4,741)	(2,470)	(3,529)	(2,094)	(29,892)	(12,834)	29,978
Scenario, Previously Reported [Member]
Revision of prior period financial statements and out-of-period adjustments (Details) - Effect of the error correction on consolidated statements of operations and comprehensive (loss) income [Line Items]
Net sales		13,928	24,038	21,891	22,744	14,661	24,166	26,052		58,559	61,260
Operating (loss) income		(378)	(18,321)	(4,025)	(3,860)	(232)	(2,928)	(1,472)		(3,432)	(1,284)
Net loss from continuing operations		(1,146)				(770)				(5,877)	35,179
Net loss from discontinued operations		(1,118)				(1,700)				(6,760)	(4,795)
Net (loss) income		(2,264)	(19,060)	(4,410)	(4,544)	(2,470)	(3,529)	(2,094)		(12,637)	30,384
Restatement Adjustment [Member]
Revision of prior period financial statements and out-of-period adjustments (Details) - Effect of the error correction on consolidated statements of operations and comprehensive (loss) income [Line Items]
Net sales		13,928	16,033	14,642	13,264	14,661	14,465	16,169
Operating (loss) income		(378)	(1,018)	(1,124)	(1,671)	(232)	(1,558)	29		245	482
Net loss from continuing operations		(1,146)	(1,757)	(1,509)	(2,355)	(770)	(2,159)	(593)		245	482
Net loss from discontinued operations		(1,118)	(17,303)	(2,901)	(2,189)	(1,700)	(1,370)	(1,501)		(48)	(76)
Net (loss) income		(2,264)	(19,060)	(4,410)	(4,544)	(2,470)	(3,529)	(2,094)		197	406
Scenario, Adjustment [Member]
Revision of prior period financial statements and out-of-period adjustments (Details) - Effect of the error correction on consolidated statements of operations and comprehensive (loss) income [Line Items]
Net sales
Operating (loss) income		(292)	(440)	(216)	(245)
Net loss from continuing operations		(292)	(440)	(216)	(245)
Net loss from discontinued operations					48
Net (loss) income		$ (292)	$ (440)	$ (216)	$ (197)