Borrowings - Narrative (Details) $ in Thousands, € in Millions		3 Months Ended	6 Months Ended	12 Months Ended
	May 08, 2018	Dec. 31, 2016 USD ($)	Apr. 01, 2017	Sep. 29, 2018 EUR (€)	Sep. 29, 2018 USD ($)	Sep. 30, 2017 EUR (€)	Sep. 30, 2017 USD ($)	Oct. 01, 2016 USD ($)	Sep. 29, 2018 USD ($)	Mar. 31, 2018 USD ($)	Nov. 07, 2016 EUR (€)	Nov. 07, 2016 USD ($)
Line of Credit Facility [Line Items]
OR laser acquisition aggregate principal of several term loans										$ 1,900
LR laser term loans principal paid off					$ 1,200
OR Laser term loans remaining aggregate principal amount									$ 600
Repayments of debt		$ 50,000
Loans assumed in business combination												$ 15,300
Aggregate amount of several lines of credit												18,100
Debt issuance cost related to repricing		500
Interest expense on Euro term loan					14,900		$ 23,500
Amortization of debt issuance cost					9,565		7,202	$ 0
Additional sources of cash available									26,500
Unused borrowing capacity									18,500
Rofin-Sinar
Line of Credit Facility [Line Items]
Maximum borrowing capacity												30,000
Swing line, maximum borrowing capacity												$ 10,000
Credit Agreement November 7 2016
Line of Credit Facility [Line Items]
Senior Secured Net leverage ratio to increase revolving commitment or borrow incremental term loan											2.75	2.75
Senior secured net leverage ratio to maintain compliance on the loan each quarter end											3.50	3.50
Euro
Line of Credit Facility [Line Items]
Domestic line of credit drawn | €											€ 10.0
Euro term loan
Line of Credit Facility [Line Items]
Debt issuance costs		28,500
Amortization period of the debt issuance cost			7 years
Amortization of debt issuance cost					$ 9,600		$ 7,200
Euro term loan | Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
Euro term loan | Eurodollar
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.25%
Gross leverage ratio	1.50
Euro term loan | Maximum | Eurodollar
Line of Credit Facility [Line Items]
Interest rate, stepdown	2.00%
Euro term loan | Minimum | Eurodollar
Line of Credit Facility [Line Items]
Interest rate, stepdown	1.00%
Euro term loan | Euro
Line of Credit Facility [Line Items]
forward contract purchased for the term loan | €				€ 371.6		€ 513.3					€ 670.0
Voluntary payment of principle | €				€ 135.0		150.0
Additional Euro currency rate											0.01	0.01
Euro currency rate range after 1st year											0.03	0.03
Euro currency rate range initially											0.035	0.035
Quarter principal payment requirement for Euro term loan											0.0025	0.0025
Euro term loan | Euro | Maximum
Line of Credit Facility [Line Items]
Euro currency rate range after 1st year											0.035	0.035
Applicable margin for Eurocurrency rate loan											0.0425	0.0425
Euro term loan | Euro | Minimum
Line of Credit Facility [Line Items]
Applicable margin for Eurocurrency rate loan											0.0375	0.0375
Revolving line of credit
Line of Credit Facility [Line Items]
Revolving facility to finance acquisition of Rofin						€ 10.0						$ 100,000
Revolving facility borrowing capacity potential increase												150,000
cash excess that requires the loan repayment												$ 10,000
Additional base rate											0.005	0.005
Base rate initially											0.025	0.025
Debt issuance costs		$ 2,300
debt issuance cost amortization period		5 years
Revolving line of credit | Maximum
Line of Credit Facility [Line Items]
Base rate range after 1st year											0.025	0.025
Applicable margin for base rate revolving loan											0.0325	0.0325
Commitment fee accrues range on unused portion of revolving loan											0.005	0.005
Revolving line of credit | Minimum
Line of Credit Facility [Line Items]
Base rate range after 1st year											0.02	0.02
Applicable margin for base rate revolving loan											0.0275	0.0275
Commitment fee accrues range on unused portion of revolving loan											0.00375	0.00375
Line of Credit, Foreign
Line of Credit Facility [Line Items]
International credit facilities as guarantees									$ 8,000