Income tax expense - Net Operating Losses (Details) - USD ($) $ in Thousands	12 Months Ended		24 Months Ended
	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016
Net operating losses carryforwards
Period in which the company is in cumulative loss position.	3 years
Valuation allowance	$ 103,185	$ 80,087	$ 103,185	$ 100,832	$ 54,114
Uncertain tax positions disclosures
Uncertain tax positions				$ 0
Ireland
Net operating losses carryforwards
Net operating losses carryforwards	187,631		187,631
Austria
Net operating losses carryforwards
Net operating losses carryforwards	223,827		223,827
U.S.
Net operating losses carryforwards
Net operating losses carryforwards	10,403		10,403
Net operating losses carryforwards	35,680		$ 35,680
U.S. federal corporate tax rate		35.00%	21.00%
Re-measurement of deferred tax assets, net	$ 800