Discontinued Operations and Sale of Assets Held for sale - Held for sale current assets and liabilities from discontinued operations (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
	Apr. 27, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jun. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non cash impairment charge to reduce carrying value of the acquired entities to fair value			$ (500)	$ 300	$ 2,900
Sale proceeds from sale of entities acquired in Rofin acquisition	$ 6,300
Loss on sale of Rofin entities		$ 500				$ 300
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash					33
Accounts receivable					6,931
Inventories					5,586
Prepaid expenses and other assets					607
Property and equipment					10,705
Intangible assets					11,400
Total current assets held for sale					35,262
Accounts payable					1,129
Other current liabilities					4,875
Total current liabilities held for sale					6,004
Continuing Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts receivable					1,668
Inventories					5,202
Prepaid expenses and other assets					472
Property and equipment					457
Intangible assets					1,187
Total current assets held for sale					8,986
Accounts payable					189
Other current liabilities					828
Total current liabilities held for sale					$ 1,017