CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Preference shares - Series A, C and D	Common shares	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit	Treasury shares	Non-controlling interests in subsidiaries
Beginning balance at Dec. 31, 2018		$ 465,000	$ 879	$ 749,418	$ (65,616)	$ (563,891)	$ (31,515)	$ 641
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options and issuance of common shares			2	(2)
Share-based compensation expense				1,722
Change in net unrealized gains (losses) on investment					78,344
Foreign currency translation adjustment					9,208			78
Net income (loss)	$ (110,376)					(110,376)
Shares repurchased							(18)
Disposal of subsidiaries								(719)
Ending balance at Sep. 30, 2019	533,155	465,000	881	751,138	21,936	(674,267)	(31,533)	0
Beginning balance at Jun. 30, 2019		465,000	881	751,007	21,152	(615,940)	(31,528)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense				131
Change in net unrealized gains (losses) on investment					(10,696)
Foreign currency translation adjustment					11,480
Net income (loss)	(58,327)					(58,327)
Shares repurchased							(5)
Ending balance at Sep. 30, 2019	533,155	465,000	881	751,138	21,936	(674,267)	(31,533)	0
Beginning balance at Dec. 31, 2019		465,000	882	751,327	17,836	(695,794)	(31,533)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options and issuance of common shares			16	(16)
Share-based compensation expense				2,013
Change in net unrealized gains (losses) on investment	6,942
Foreign currency translation adjustment					(10,821)
Net income (loss)	32,235					32,235
Shares repurchased							(1)
Ending balance at Sep. 30, 2020	538,086	465,000	898	753,324	13,957	(663,559)	(31,534)	0
Beginning balance at Jun. 30, 2020		465,000	897	752,896	9,201	(665,721)	(31,534)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options and issuance of common shares			1	(1)
Share-based compensation expense				429
Change in net unrealized gains (losses) on investment					11,754
Foreign currency translation adjustment					(6,998)
Net income (loss)	2,162					2,162
Ending balance at Sep. 30, 2020	$ 538,086	$ 465,000	$ 898	$ 753,324	$ 13,957	$ (663,559)	$ (31,534)	$ 0