Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows provided by operating activities
Net income	$ 320,497	$ 279,940
Adjustments to reconcile net income to cash provided by operating activities:
Share compensation expenses	21,964	18,296
Amortization of discount on senior notes	54	54
Loss (income) from investment affiliate	4,702	(3,060)
Net realized gains on investments	(2,140)	(6,413)
Change in net unrealized (gains) losses on investments	(78,872)	1,449
Amortization of intangible assets	2,832	2,832
Loss (income) from operating affiliates	23	(5,722)
Foreign exchange (gains) losses included in net income	(6,289)	7,729
Amortization of premium on fixed maturities	8,710	12,395
Change in:
Premiums receivable	(719,070)	(566,100)
Deferred acquisition costs	(102,211)	(92,020)
Prepaid reinsurance premiums	(67,575)	(79,304)
Loss reserves recoverable	(95,429)	644
Paid losses recoverable	(4,571)	(2,253)
Income taxes recoverable	7,423	(13,931)
Deferred tax asset	(2,529)	908
Accrued investment income	(1,183)	984
Other assets	(5,272)	90,625
Reserve for losses and loss expenses	147,305	(50,240)
Unearned premiums	655,353	529,374
Reinsurance balances payable	18,610	(34,472)
Deferred tax liability	(308)	2,329
Accounts payable and accrued expenses	(32,581)	(61,570)
Net cash provided by operating activities	69,443	32,474
Cash flows used in investing activities
Proceeds on sales of fixed maturity investments	1,376,077	2,237,966
Proceeds on maturities of fixed maturity investments	184,413	186,594
Purchases of fixed maturity investments	(1,537,608)	(2,337,990)
Purchases of short-term investments, net	(428,040)	(154,804)
(Purchases) sales of other investments, net	(19,796)	4,101
Increase in securities lending collateral	(5,361)	(6,551)
Redemption from operating affiliates	369	0
(Increase) decrease in restricted cash	(22,752)	32,984
Net cash used in investing activities	(469,003)	(60,815)
Cash flows provided by (used in) financing activities
Net proceeds on issuance of notes payable to AlphaCat investors	294,748	0
Net proceeds on issuance of preferred shares	144,852	0
Issuance of common shares, net	(7,385)	14,860
Purchases of common shares under share repurchase program	(129,083)	(143,223)
Dividends paid on preferred shares	0	0
Dividends paid on common shares	(59,961)	(58,718)
Increase in securities lending payable	5,361	6,551
Third party investment in redeemable noncontrolling interest	381,250	452,700
Third party redemption of redeemable noncontrolling interest	(10,800)	(80,433)
Third party investment in noncontrolling interest	171,674	9,600
Third party distributions of noncontrolling interest	(127,103)	(158,175)
Third party subscriptions deployed on AlphaCat Funds and Sidecars	(411,336)	(117,400)
Net cash provided by (used in) financing activities	252,217	(74,238)
Effect of foreign currency rate changes on cash and cash equivalents	(6,968)	(8,730)
Net decrease in cash and cash equivalents	(154,311)	(111,309)
Cash and cash equivalents - beginning of period	723,109	550,401
Cash and cash equivalents - end of period	568,798	439,092
Taxes paid during the period	3,837	14,192
Interest paid during the period	27,552	27,248
Investment affiliate
Adjustments to reconcile net income to cash provided by operating activities:
Loss (income) from investment affiliate	4,702	(3,060)
Cash flows used in investing activities
Investment in investment affiliates, net	$ (16,305)	$ (23,115)