Quarterly financial information (unaudited) - Schedule of Historical Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 143,833	$ 132,825	$ 164,023	$ 195,796	$ 151,782	$ 142,812	$ 145,572	$ 176,847	$ 636,477	$ 617,013	$ 559,545
Operating (loss) income	(15,403)	(16,458)	10,334	47,237	13,788	2,984	18,719	55,106	25,710	90,597	88,669
Net (loss) income	(17,924)	(30,461)	1,040	42,988	(14,239)	(5,422)	16,821	21,817	(4,357)	18,977	(241)
Net (loss) income available to ordinary shareholders	$ (17,924)	$ (30,461)	$ 1,040	$ 42,988	$ (14,239)	$ (5,422)	$ 16,821	$ 21,817	$ (4,357)	$ 18,977	$ (9,042)
(Losses) earnings per share - basic (in dollars per share)	$ (0.14)	$ (0.23)	$ 0.01	$ 0.33	$ (0.11)	$ (0.04)	$ 0.14	$ 0.20	$ (0.03)	$ 0.16	$ (0.09)
(Losses) earnings per share - diluted (in dollars per share)	$ (0.14)	$ (0.23)	$ 0.01	$ 0.33	$ (0.11)	$ (0.04)	$ 0.14	$ 0.20	$ (0.03)	$ 0.16	$ (0.09)