Summary of Tax Returns Periods Subject to Examination by Federal, State and International Tax Authorities (Detail)	6 Months Ended
	Jun. 30, 2018
Germany
Income Tax Examination [Line Items]
Fiscal year subject to examination	2017
Earliest Tax Year | United States
Income Tax Examination [Line Items]
Fiscal year subject to examination	2014
Earliest Tax Year | Sweden
Income Tax Examination [Line Items]
Fiscal year subject to examination	2011
Earliest Tax Year | Netherlands
Income Tax Examination [Line Items]
Fiscal year subject to examination	2012
Latest Tax Year | United States
Income Tax Examination [Line Items]
Fiscal year subject to examination	2017
Latest Tax Year | Sweden
Income Tax Examination [Line Items]
Fiscal year subject to examination	2017
Latest Tax Year | Netherlands
Income Tax Examination [Line Items]
Fiscal year subject to examination	2017