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	$ 100,832	$ 80,087	$ 54,114	$ 40,487
Uncertain tax positions disclosures
Uncertain tax positions	0	$ 0
Ireland
Net operating losses carryforwards
Net operating losses carryforwards	107,671
Austria
Net operating losses carryforwards
Net operating losses carryforwards	259,229
U.S.
Net operating losses carryforwards
Net operating losses carryforwards	$ 44,728
U.S. federal corporate tax rate	21.00%	35.00%
Re-measurement of deferred tax assets, net	$ 800