Operating Segments - Profit by Reportable Segment to Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total profit from segments	$ (8,771)	$ 1,491	$ (11,773)	$ (1,747)
Depreciation			(7,755)	(8,787)
General and administrative	(5,866)	(1,669)	(9,101)	(5,961)
Advisory fee to related party	(5,739)	(2,353)	(8,175)	(4,726)
Other income	909	3,176	2,376	4,864
Interest income	5,616	5,284	11,260	11,038
Interest expense	(7,681)	(9,071)	(15,419)	(18,673)
(Loss) gain on foreign currency transaction			2,824	2,244
Income (losses) from unconsolidated joint ventures	4,572	(719)	7,908	(979)
(Loss) gain on sales or write-down of assets	(24,445)	5,339	(7,047)	9,477
Income tax expense	1,841	(49)	1,801	(296)
Net (loss) income	(33,661)	(3,324)	(10,446)	1,064
Operating segments
Segment Reporting Information [Line Items]
Total profit from segments	5,136	5,755	9,665	10,888
Other non-segment items of income (expense)
Segment Reporting Information [Line Items]
Depreciation	(3,211)	(3,418)	(6,538)	(6,812)
General and administrative	(5,866)	(1,669)	(9,101)	(5,961)
Advisory fee to related party	(5,739)	(2,353)	(8,175)	(4,726)
Other income	5,616	5,284	2,376	4,864
Interest income	909	3,176	11,260	11,038
Interest expense	(7,681)	(9,071)	(15,419)	(18,673)
(Loss) gain on foreign currency transaction	(4,793)	(5,599)	2,824	2,244
Income (losses) from unconsolidated joint ventures	4,572	(719)	7,908	(979)
(Loss) gain on sales or write-down of assets	(24,445)	5,339	(7,047)	9,477
Income tax expense	1,841	(49)	1,801	(296)
Net (loss) income	$ (33,661)	$ (3,324)	$ (10,446)	$ 1,064