Income Taxes (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Income Tax Contingency [Line Items]
Statutory income tax rate	19.30%	34.40%	19.30%	34.40%
Effective tax rate	48.60%	25.40%	48.80%	22.60%
Domestic Tax Authority | Her Majesty's Revenue and Customs (HMRC)
Income Tax Contingency [Line Items]
Statutory income tax rate			19.30%
Domestic Tax Authority | Ministry of the Economy, Finance and Industry, France
Income Tax Contingency [Line Items]
Statutory income tax rate					34.40%