Accrued liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued liabilities [Abstract]
Accrued development costs	$ 50,957	$ 16,631
Accrued interest	55,253	27,938
Accrued consideration in asset acquisitions	18,660	0
Accrued bonuses	12,067	17,344
Accrued vessel operating and drydocking expenses	4,575	0
Other accrued expenses	51,211	28,439
Total accrued liabilities	$ 192,723	$ 90,352