Taxation - Summary of valuation allowance (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Valuation Allowance [Line Items]
Valuation allowance	$ 338,556	$ 367,366
Australia
Valuation Allowance [Line Items]
Valuation allowance	18,849	15,120
Austria
Valuation Allowance [Line Items]
Valuation allowance	919	10,162
Brazil
Valuation Allowance [Line Items]
Valuation allowance	14,909	12,857
France
Valuation Allowance [Line Items]
Valuation allowance	28,656	23,523
Germany
Valuation Allowance [Line Items]
Valuation allowance	32,566	9,562
Hong Kong
Valuation Allowance [Line Items]
Valuation allowance	5,749	3,780
Ireland
Valuation Allowance [Line Items]
Valuation allowance	86,647	96,642
Italy
Valuation Allowance [Line Items]
Valuation allowance	0	10,313
Luxembourg
Valuation Allowance [Line Items]
Valuation allowance	8,025	5,648
Singapore
Valuation Allowance [Line Items]
Valuation allowance	9,331	8,916
Spain
Valuation Allowance [Line Items]
Valuation allowance	20,387	16,709
Switzerland
Valuation Allowance [Line Items]
Valuation allowance	20,935	15,025
United Kingdom
Valuation Allowance [Line Items]
Valuation allowance	28,328	32,528
United States
Valuation Allowance [Line Items]
Valuation allowance	53,761	92,999
Other
Valuation Allowance [Line Items]
Valuation allowance	$ 9,494	$ 13,582