Income Taxes - Tax Jurisdictions and Years Currently under Audit Exam (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2018
Income Tax Examination [Line Items]
Estimated benefit to tax expense		$ 25
UNITED STATES | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam			2015
UNITED STATES | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam			2016
BELGIUM | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2015
BELGIUM | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2016
CHINA | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2008
CHINA | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2016
France | Tax Year 2010 [Member]
Income Tax Examination [Line Items]
Tax years currently under audit exam	2010
France | Tax Year 2011 [Member]
Income Tax Examination [Line Items]
Tax years currently under audit exam	2011
France | Tax Year 2012 [Member]
Income Tax Examination [Line Items]
Tax years currently under audit exam	2012
France | Tax Year 2015 [Member]
Income Tax Examination [Line Items]
Tax years currently under audit exam	2015
France | Tax Year 2016 [Member]
Income Tax Examination [Line Items]
Tax years currently under audit exam	2016
Germany | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2007
Germany | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2015
SPAIN | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2010
SPAIN | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2012
SWITZERLAND | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2011
SWITZERLAND | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2014
United Kingdom | Earliest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2011
United Kingdom | Latest tax year under exam
Income Tax Examination [Line Items]
Tax years currently under audit exam	2015