Summary of Tax Returns Periods Subject to Examination by Federal, State and International Taxing Authorities (Detail)	6 Months Ended
	Jun. 30, 2017
United States | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Fiscal year subject to examination	2013
United States | Latest Tax Year
Income Tax Examination [Line Items]
Fiscal year subject to examination	2016
Sweden | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Fiscal year subject to examination	2011
Sweden | Latest Tax Year
Income Tax Examination [Line Items]
Fiscal year subject to examination	2016
Germany | Latest Tax Year
Income Tax Examination [Line Items]
Fiscal year subject to examination	2016