Income Taxes - Components of provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Provision for income tax benefit (expense)
Current	$ 8,520	$ 5,222	$ 10,561
Income tax provision	$ (8,520)	$ (5,222)	$ (10,561)
Effective tax rate (as a percent)	2.97%	2.16%	4.67%
Provision for income taxes on undistributed earnings of foreign subsidiaries	$ 0
Undistributed earnings	0
United States
Provision for income tax benefit (expense)
Current	8,545	$ 5,210	$ 10,563
Ireland
Provision for income tax benefit (expense)
Current	$ (13)
Effective tax rate (as a percent)	2.97%	2.16%	4.67%
United Kingdom
Provision for income tax benefit (expense)
Current	$ (12)	$ 12	$ (2)