Income Taxes - Components of provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Provision for income tax benefit (expense)
Current	$ 5,222	$ 10,561	$ (13,694)
Total	$ 5,222	$ 10,561	$ (13,694)
Effective tax rate (as a percent)	2.16%	4.67%	(5.04%)
Provision for income taxes on undistributed earnings of foreign subsidiaries	$ 0
Undistributed earnings	0
United States
Provision for income tax benefit (expense)
Current	$ 5,210	$ 10,563	$ (13,091)
Ireland
Provision for income tax benefit (expense)
Current			$ (566)
Effective tax rate (as a percent)	2.16%	4.67%	(5.04%)
United Kingdom
Provision for income tax benefit (expense)
Current	$ 12	$ (2)	$ (37)