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Nominal or face amount used to calculate payments on the derivative asset.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Derivative Instruments and Hedging Activities - Notional and Fair Value (Details) $ in Thousands, € in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2018 USD ($)	Apr. 01, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 01, 2016 USD ($)	Mar. 31, 2018 USD ($)	Apr. 01, 2017 USD ($)	Mar. 31, 2018 EUR (€)	Mar. 31, 2018 USD ($)	Sep. 30, 2017 USD ($)	Nov. 07, 2016 EUR (€)	Aug. 01, 2016 EUR (€)	Aug. 01, 2016 USD ($)
Derivatives, Fair Value [Line Items]
Gain (loss) on derivatives	$ 1,000	$ (100)			$ (1,600)	$ 9,400
Purchase \| Not Designated as Hedging Instrument \| Euro Member Countries, Euro
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount								$ 158,947	$ 109,641
Derivative asset, Fair Value								294	1,397
Purchase \| Not Designated as Hedging Instrument \| Japan, Yen
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount								760	0
Derivative asset, Fair Value								(5)	0
Sell \| Not Designated as Hedging Instrument \| Japan, Yen
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount								(33,521)	(25,126)
Derivative liability, Fair Value								(218)	591
Sell \| Not Designated as Hedging Instrument \| Korea (South), Won
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount								(32,641)	(28,996)
Derivative liability, Fair Value								(380)	551
Sell \| Not Designated as Hedging Instrument \| China, Yuan Renminbi
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount								(47,307)	(13,744)
Derivative liability, Fair Value								(565)	128
Foreign currency contracts
Derivatives, Fair Value [Line Items]
Term loan obtain at Rofin acquisition												$ 750,000
Unrealized gain (loss) on derivatives				$ (2,200)
Net gain from forward contracts settlement			$ 9,100
Derivative, gain (loss) on derivative, net			$ 11,300
Other Foreign Currency Hedge \| Purchase \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount								10,096	3,668
Derivative asset, Fair Value								(65)	4
Other Foreign Currency Hedge \| Sell \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount								(1,637)	(2,971)
Derivative liability, Fair Value								$ (32)	$ (74)
Euro term loan \| Euro Member Countries, Euro
Derivatives, Fair Value [Line Items]
forward contract purchased for the term loan \| €							€ 375.0			€ 670.0	€ 670.0