CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net income (loss)		$ 35,615	$ (24,242)	$ 7,331
Other comprehensive income (loss):
Foreign currency translation adjustments, net of tax	[1]	(4,083)	(6,968)	54
Pension liability adjustments, net of tax	[2]	1,709	(3,146)	3,353
Total other comprehensive income (loss)		(2,374)	(10,114)	3,407
Total consolidated comprehensive income (loss)		33,241	(34,356)	10,738
Less: Comprehensive income attributable to noncontrolling interest			(10)	(22)
Comprehensive income (loss) attributable to GSI Group Inc.		$ 33,241	$ (34,366)	$ 10,716

[1] The tax effect on this component of comprehensive income was $193, $622 and $477 in 2015, 2014 and 2013, respectively.

[2] The tax effect on this component of comprehensive income was $307, ($906) and $900 in 2015, 2014 and 2013, respectively.