Income Taxes - Components of income tax provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income (loss) before provision for income taxes
Bermuda	$ (161,983)	$ (168,053)	$ (105,562)
Foreign	5,754	4,139	2,121
Income (loss) before provision for income taxes	(156,229)	(163,914)	(103,441)
Current income tax (provision):
U.S. federal	(392)	(567)	(547)
U.S. state	(366)	(530)	(217)
Foreign	(33)	(12)
Total current income tax (provision)	(791)	(1,109)	(764)
Deferred income tax benefit:
U.S. federal	(3,056)	2,397	542
U.S. state	(1,315)	759	436
Foreign	10
Total deferred income tax benefit	(4,361)	3,156	978
Total provision (benefit) for income taxes	$ (5,152)	$ 2,047	$ 214