Restructuring charges (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Jun. 30, 2018	Jul. 01, 2017
Restructuring Reserve [Roll Forward]
Starting balance	$ 933	$ 1,175	$ 1,301	$ 1,965	$ 2,359	$ 0	$ 1,301	$ 0
Provision	1,193	726	1,164	1,500	557	7,062
Payments and other	(1,113)	(968)	(1,290)	(2,005)	(951)	(4,703)
Ending balance	1,013	933	1,175	1,460	1,965	2,359	1,013	1,460
Severance Related
Restructuring Reserve [Roll Forward]
Starting balance	933	1,175	1,301	1,786	2,359	0	1,301	0
Provision	306	599	629	1,115	319	2,703
Payments and other	(415)	(841)	(755)	(1,793)	(892)	(344)
Ending balance	824	933	1,175	1,108	1,786	2,359	824	1,108
Severance Related \| Industrial Lasers & Systems
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	1,000			1,500			2,000	8,600
Severance Related \| OEM Laser Sources
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	200			0			1,100	500
Severance Related \| Other current liabilities:
Restructuring Reserve [Roll Forward]
Ending balance	1,000						1,000
Asset Write-Offs
Restructuring Reserve [Roll Forward]
Starting balance	0	0	0	0	0	0	0	0
Provision	1,221	9	430	82	(45)	4,359
Payments and other	(1,221)	(9)	(430)	(82)	45	(4,359)
Ending balance	0	0	0	0	0	0	0	0
Other
Restructuring Reserve [Roll Forward]
Starting balance	0	0	0	179	0	0	0	0
Provision	(334)	118	105	303	283	0
Payments and other	523	(118)	(105)	(130)	(104)	0
Ending balance	$ 189	$ 0	$ 0	$ 352	$ 179	$ 0	$ 189	$ 352

Restructuring related payment and other during the period

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

+ Details

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- Definition

Carrying amount as of the balance sheet date of known and estimated obligations associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, which are expected to be paid in the next twelve months or in the normal operating cycle if longer. Costs of such activities include those for one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, relocating employees, and costs associated with an ongoing benefit arrangement, but excludes costs associated with the retirement of a long-lived asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b)(2))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) in the accrual for restructuring costs.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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