CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Ordinary share capital	Additional paid-in capital	Retained earnings	Shareholders' equity attributable to shareholders	Non-controlling interest in joint venture
Beginning balance at Dec. 31, 2014	$ 1,179,384	$ 3,738	$ 500,553	$ 660,860	$ 1,165,151	$ 14,233
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of Class A ordinary shares, net of forfeitures	26	26	0	0	26	0
Repurchase of Class A ordinary shares	(17,692)	(61)	(8,483)	(9,148)	(17,692)	0
Share-based compensation expense, net of forfeitures	4,248	0	4,248	0	4,248	0
Short-swing sale profit from shareholder	83	0	83	0	83	0
Change in non-controlling interest in related party joint venture	(3,115)	0	0	0	0	(3,115)
Net income (loss)	(326,425)	0	0	(326,425)	(326,425)	0
Ending balance at Dec. 31, 2015	836,509	3,703	496,401	325,287	825,391	11,118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of Class A ordinary shares, net of forfeitures	34	34	0	0	34	0
Share-based compensation expense, net of forfeitures	3,936	0	3,936	0	3,936	0
Change in non-controlling interest in related party joint venture	443	0	0	0	0	443
Net income (loss)	44,881	0	0	44,881	44,881	0
Ending balance at Dec. 31, 2016	885,803	3,737	500,337	370,168	874,242	11,561
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of Class A ordinary shares, net of forfeitures	13	13	0	0	13	0
Repurchase of Class A ordinary shares	(2,819)	(14)	(1,861)	(944)	(2,819)	0
Share-based compensation expense, net of forfeitures	4,840	0	4,840	0	4,840	0
Change in non-controlling interest in related party joint venture	1,372	0	0	0	0	1,372
Net income (loss)	(44,952)	0	0	(44,952)	(44,952)	0
Ending balance at Dec. 31, 2017	$ 844,257	$ 3,736	$ 503,316	$ 324,272	$ 831,324	$ 12,933