Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows provided by (used in) operating activities
Net income	$ 66,462	$ 139,336
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Share compensation expenses	9,729	9,491
Amortization of discount on senior notes	27	27
(Income) from investment and operating affiliates	(13,068)	(5,188)
Net realized and change in net unrealized losses (gains) on investments	55,181	(12,184)
Amortization of intangible assets	2,243	1,416
Foreign exchange (gains) included in net income	(9,885)	(4,938)
Amortization of premium on fixed maturities	3,899	3,536
Change in:
Premiums receivable	(924,817)	(488,653)
Deferred acquisition costs	(96,009)	(82,953)
Prepaid reinsurance premiums	(257,962)	(121,050)
Loss reserves recoverable	255,701	(20,743)
Paid losses recoverable	(13,069)	(2,619)
Reserve for losses and loss expenses	(207,632)	53,436
Unearned premiums	1,095,182	536,425
Reinsurance balances payable	66,720	63,070
Other operational balance sheet items, net	13,240	(50,610)
Net cash provided by operating activities	45,942	17,799
Cash flows provided by (used in) investing activities
Proceeds on sales of fixed maturity investments	785,662	743,631
Proceeds on maturities of fixed maturity investments	166,651	123,269
Purchases of fixed maturity investments	(963,990)	(676,349)
Purchases (sales) of short-term investments, net	(257,214)	11,030
Purchases of other investments, net	(1,137)	(34,295)
Decrease (increase) in securities lending collateral	(1,493)	(607)
(Investments in) distributions from investment affiliates, net	(266)	10,922
Net cash (used in) provided by investing activities	(271,787)	177,601
Cash flows provided by (used in) financing activities
Net proceeds on issuance of notes payable to AlphaCat investors	155,966	73,048
Redemption of common shares, net	(12)	(167)
Dividends paid on preferred shares	(5,828)	(2,203)
Dividends paid on common shares	(31,032)	(30,092)
(Decrease) increase in securities lending payable	1,493	607
Third party investment in redeemable noncontrolling interests	385,300	103,699
Third party redemption of redeemable noncontrolling interests	(173,986)	(68,296)
Third party investment in noncontrolling interests	281,300	154,980
Third party distributions of noncontrolling interests	0	(62,770)
Third party subscriptions deployed in AlphaCat Funds and Sidecars	(578,666)	(144,452)
Net cash provided by financing activities	34,535	24,354
Effect of foreign currency rate changes on cash and cash equivalents and restricted cash	16,107	5,798
Net (decrease) increase in cash and cash equivalents and restricted cash	(175,203)	225,552
Cash and cash equivalents and restricted cash—beginning of period	1,149,653	490,932
Cash and cash equivalents and restricted cash—end of period	974,450	716,484
Supplemental disclosure of cash flow information:
Taxes paid during the period	460	16
Interest paid during the period	$ 19,068	$ 19,073