CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 03, 2015	Jun. 27, 2014	Jul. 03, 2015	Jun. 27, 2014
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net income		$ 19,498	$ 728	$ 22,944	$ 1,718
Other comprehensive income (loss):
Foreign currency translation adjustments, net of tax	[1]	3,958	1,006	(548)	943
Pension liability adjustments, net of tax	[2]	(309)	(50)	420	14
Total other comprehensive income (loss)		3,649	956	(128)	957
Total consolidated comprehensive income (loss)		23,147	1,684	22,816	2,675
Less: Comprehensive income attributable to noncontrolling interest			(3)		(10)
Comprehensive income (loss) attributable to GSI Group Inc.		$ 23,147	$ 1,681	$ 22,816	$ 2,665

[1] The tax effect on this component of comprehensive income was $0.5 million for the three and six months ended July 3, 2015 and $0.2 million for the three and six months ended June 27, 2014.

[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).