CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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
Net change in unrealized gains and losses on investments and financial contracts	41,444	(209,993)	265,401
Net realized (gains) losses on investments and financial contracts	(87,618)	113,836	(22,227)
Foreign exchange (gains) losses on restricted cash and investments	5,292	3,094	6,225
Income (loss) attributable to total non-controlling interest in related party joint venture	578	1,819	(5,508)
Share-based compensation expense, net of forfeitures	4,853	3,970	4,274
Depreciation expense	368	390	405
Net change in
Reinsurance balances receivable	(82,636)	(31,186)	(83,113)
Loss and loss adjustment expenses recoverable	(26,755)	664	(916)
Deferred acquisition costs, net	(1,328)	(1,199)	(25,403)
Unearned premiums ceded	(22,743)	874	776
Other assets	705	2,171	(1,791)
Loss and loss adjustment expense reserves	(157,739)	(644)	(41,754)
Unearned premium reserves	33,291	10,573	83,218
Reinsurance balances payable	102,643	23,089	7,524
Funds withheld	17,652	(1,216)	585
Other liabilities	(4,114)	1,802	(2,224)
Net cash provided by (used in) operating activities	94,419	(35,787)	(57,445)
Investing activities
Purchases of investments, trading	(1,120,549)	(1,310,837)	(1,252,969)
Sales of investments, trading	1,036,665	1,470,118	1,388,162
Payments for financial contracts	(24,714)	(60,414)	(25,765)
Proceeds from financial contracts	82,789	20,426	7,002
Securities sold, not yet purchased	1,120,506	699,237	892,085
Dispositions of securities sold, not yet purchased	(1,253,176)	(792,970)	(1,068,891)
Change in due to prime brokers and other financial institutions	352,870	(76,623)	185,383
Change in restricted cash and cash equivalents, net	(308,241)	36,972	50,400
Change in notes receivable, net	5,237	(8,588)	2,279
Non-controlling interest contribution into (withdrawal from) related party joint venture, net	2,079	(7,756)	0
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)
Effect of foreign exchange rate changes on cash and cash equivalents	2,361	(6,082)	(2,500)
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	12,030
Cash and cash equivalents at end of the period	27,285	39,858	112,162
Supplementary information
Interest paid in cash	10,062	7,823	21,959
Income tax paid in cash	0	0	0
Non-cash transfer to notes receivable	$ 0	$ 0	$ 25,859