Income tax (expense) benefit - Net operating losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net operating losses carryforwards
Valuation allowance		$ 80,087	$ 54,114	$ 40,487
Uncertain tax positions disclosures
Uncertain tax positions		0	$ 0
Ireland
Net operating losses carryforwards
Net operating losses carryforwards		27,490
Austria
Net operating losses carryforwards
Net operating losses carryforwards		268,285
U.S.
Net operating losses carryforwards
Net operating losses carryforwards		200
Re-measurement of deferred tax assets, net		$ 800
U.S. federal corporate tax rate		35.00%
U.S. | Forecast
Net operating losses carryforwards
U.S. federal corporate tax rate	21.00%