Income Taxes Tax Jurisdictions and Years Currently under Audit Exam (Details)	12 Months Ended
	Sep. 30, 2018
Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Expiration period of net operating loss carryforwards	Dec. 31, 2019
Latest Tax Year [Member]
Income Tax Examination [Line Items]
Expiration period of net operating loss carryforwards	Dec. 31, 2038
UNITED STATES | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2015
UNITED STATES | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2016
Belgium | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2015
Belgium | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2017
CHINA | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2008
CHINA | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2016
France | Tax Year 2010 [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2010
France | Tax Year 2011 [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2011
France | Tax Year 2012 [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2012
France | Tax Year 2015 [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2015
France | Tax Year 2016 [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2016
Germany | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2007
Germany | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2016
SPAIN | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2010
SPAIN | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2012
United Kingdom | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2012
United Kingdom | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Tax jurisdictions and years currently under audit exam	2015