Acquisitions - Defined Benefit Plan (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Apr. 06, 2018	Sep. 30, 2017
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Plan assets	$ 6,574	$ 7,078		$ 2,225
Accrued benefit obligation	(5,341)	(4,066)
Plan liability	$ 11,915	$ 11,144		$ 3,565
Tec-Sem Group AG
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Plan assets			$ 5,100
Accrued benefit obligation			2,800
Plan liability			$ 7,900
Defined benefit plan, type			us-gaap:PensionPlansDefinedBenefitMember
Defined benefit plan, sponsor location			us-gaap:ForeignPlanMember country:CH