CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Sales	$ 366,280	$ 383,516	$ 254,388
Cost of goods sold	205,900	217,115	155,842
Gross profit	160,380	166,401	98,546
Operating expenses:
Research and development and engineering	31,966	29,857	28,254
Selling, general and administrative	78,360	74,880	60,422
Amortization of purchased intangible assets	3,515	4,436	5,805
Impairment of goodwill and intangible assets			1,045
Restructuring, restatement related costs and other	2,304	2,592	16,291
Pre-petition and post-emergence professional fees	296	727	6,966
Total operating expenses	116,441	112,492	118,783
Income (loss) from operations	43,939	53,909	(20,237)
Interest income	92	87	294
Interest expense	(13,062)	(19,908)	(27,751)
Foreign exchange transaction (losses) gains, net	(95)	328	(816)
Other income (expense), net	1,183	1,840	206
Income (loss) from continuing operations before reorganization items and income taxes	32,057	36,256	(48,304)
Reorganization items		(26,156)	(23,606)
Income (loss) from continuing operations before income taxes	32,057	10,100	(71,910)
Income tax provision (benefit)	3,056	10,739	(773)
Income (loss) from continuing operations	29,001	(639)	(71,137)
Loss from discontinued operations, net of tax			(132)
Consolidated net income (loss)	29,001	(639)	(71,269)
Less: Net income attributable to noncontrolling interest	(28)	(48)	(61)
Net income (loss)	28,973	(687)	(71,330)
Income (loss) from continuing operations attributable to GSI Group Inc. per common share:
Basic	$ 0.87	$ (0.03)	$ (4.47)
Diluted	$ 0.86	$ (0.03)	$ (4.47)
Loss from discontinued operations attributable to GSI Group Inc. per common share:
Basic			$ (0.01)
Diluted			$ (0.01)
Net income (loss) attributable to GSI Group Inc. per common share:
Basic	$ 0.87	$ (0.03)	$ (4.48)
Diluted	$ 0.86	$ (0.03)	$ (4.48)
Weighted average common shares outstanding-basic	33,481	23,703	15,916
Weighted average common shares outstanding-diluted	33,589	23,703	15,916
Amounts attributable to GSI Group Inc.:
Income (loss) from continuing operations	28,973	(687)	(71,198)
Loss from discontinued operations			(132)
Net income (loss)	$ 28,973	$ (687)	$ (71,330)