CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 02, 2015	Sep. 26, 2014	Oct. 02, 2015	Sep. 26, 2014
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net income		$ 6,568	$ 4,525	$ 29,512	$ 6,243
Other comprehensive income (loss):
Foreign currency translation adjustments, net of tax	[1]	(1,624)	(3,845)	(2,172)	(2,902)
Pension liability adjustments, net of tax	[2]	517	435	937	449
Total other comprehensive income (loss)		(1,107)	(3,410)	(1,235)	(2,453)
Total consolidated comprehensive income (loss)		5,461	1,115	28,277	3,790
Less: Comprehensive income attributable to noncontrolling interest					(10)
Comprehensive income (loss) attributable to GSI Group Inc.		$ 5,461	$ 1,115	$ 28,277	$ 3,780

[1] The tax effect on this component of comprehensive income was $0.2 million for the three and nine months ended October 2, 2015. The impact was $0.4 million and $0.2 million for the three and nine months ended September 26, 2014, respectively.

[2] The tax effect on this component of comprehensive income was not material for all periods presented. See Note 4 for the total amount of pension liability adjustments reclassified out of accumulated other comprehensive income (loss).