SCHEDULE II Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash provided by (used in) operating activities
Net income (loss)	$ 37,732	$ (19,875)	$ 35,469	$ (8,374)	$ (49,196)	$ (30,011)	$ 62,995	$ (28,669)	$ 44,952	$ (44,881)	$ 326,425
Adjustments to reconcile net income or loss to net cash provided by (used in) operating activities
Share-based compensation expense, net of forfeitures									4,853	3,970	4,274
Net change in
Net cash (used in) provided by operating activities									94,419	(35,787)	(57,445)
Investing activities
Change in notes receivable, net									5,237	(8,588)	2,279
Net cash provided by (used in) investing activities									(106,534)	(30,435)	177,686
Financing activities
Short-swing sale profit from shareholder									0	0	83
Repurchase of Class A ordinary shares									(2,819)	0	(17,692)
Net cash provided by (used in) financing activities									(2,819)	0	(17,609)
Net increase (decrease) in cash and cash equivalents									(12,573)	(72,304)	100,132
Cash and cash equivalents at beginning of the period				39,858				112,162	39,858	112,162	12,030
Cash and cash equivalents at end of the period	27,285				39,858				27,285	39,858	112,162
Parent Company
Cash provided by (used in) operating activities
Net income (loss)									44,952	(44,881)	326,425
Adjustments to reconcile net income or loss to net cash provided by (used in) operating activities
Equity in earnings of consolidated subsidiaries									74,748	(47,971)	328,339
Share-based compensation expense, net of forfeitures									4,691	4,042	4,048
Net change in
Due from subsidiaries									(876)	0	15,276
Due to subsidiaries									(29,023)	12,037	16,986
Net cash (used in) provided by operating activities									4,588	12,989	38,450
Investing activities
Change in notes receivable, net									(191)	(12,989)	(609)
Contributed surplus to subsidiaries, net									1,500	0	20,000
Net cash provided by (used in) investing activities									(1,691)	(12,989)	(20,836)
Financing activities
Short-swing sale profit from shareholder									0	0	83
Net cash provided by (used in) financing activities									(2,819)	0	(17,609)
Net increase (decrease) in cash and cash equivalents									78	0	5
Cash and cash equivalents at beginning of the period				$ 6				$ 6	6	6	1
Cash and cash equivalents at end of the period	$ 84				$ 6				84	6	6
Non cash consideration from (to) subsidiaries, net									(162)	72	(227)
Common Class A [Member] | Parent Company
Financing activities
Repurchase of Class A ordinary shares									$ (2,819)	$ 0	$ (17,692)