Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows provided by operating activities
Net income	$ 450,032	$ 372,819
Adjustments to reconcile net income to cash provided by operating activities:
Share compensation expenses	32,465	28,279
Amortization of discount on senior notes	81	81
Loss (income) from investment affiliate	4,249	(5,542)
Net realized gains on investments	(6,537)	(5,226)
Change in net unrealized gains on investments	(84,331)	(2,467)
Amortization of intangible assets	4,248	4,248
Loss from operating affiliates	23	2,241
Foreign exchange (gains) losses included in net income	(4,585)	16,549
Amortization of premium on fixed maturities	13,381	17,866
Change in:
Premiums receivable	(288,048)	(356,734)
Deferred acquisition costs	(68,920)	(63,960)
Prepaid reinsurance premiums	(41,813)	(43,331)
Loss reserves recoverable	(97,742)	(9,111)
Paid losses recoverable	(13,165)	16,408
Income taxes recoverable	9,034	(16,088)
Deferred tax asset	(4,885)	1,390
Accrued investment income	(1,231)	1,059
Other assets	(83,068)	41,998
Reserve for losses and loss expenses	66,561	(61,691)
Unearned premiums	393,228	292,090
Reinsurance balances payable	2,726	(38,284)
Deferred tax liability	(593)	3,323
Accounts payable and accrued expenses	(26,514)	(49,057)
Net cash provided by operating activities	254,596	146,860
Cash flows used in investing activities
Proceeds on sales of fixed maturity investments	2,047,496	2,888,919
Proceeds on maturities of fixed maturity investments	256,082	260,179
Purchases of fixed maturity investments	(2,317,674)	(3,169,834)
Purchases of short-term investments, net	(540,102)	(226,316)
Purchases of other investments, net	(53,627)	(6,065)
Increase in securities lending collateral	(5,766)	(5,991)
Redemption from operating affiliates	369	0
(Increase) decrease in restricted cash	(39,778)	99,001
Net cash used in investing activities	(669,307)	(179,193)
Cash flows provided by (used in) financing activities
Net proceeds on issuance of notes payable to AlphaCat investors	296,527	75,607
Net proceeds on issuance of preferred shares	144,852	0
Issuance of common shares, net	(7,631)	16,735
Purchases of common shares under share repurchase program	(196,015)	(203,917)
Dividends paid on preferred shares	(2,252)	0
Dividends paid on common shares	(87,901)	(86,401)
Increase in securities lending payable	5,766	5,991
Third party investment in redeemable noncontrolling interest	381,950	497,700
Third party redemption of redeemable noncontrolling interest	(17,284)	(86,933)
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	(412,736)	(161,900)
Net cash provided by (used in) financing activities	149,847	(91,693)
Effect of foreign currency rate changes on cash and cash equivalents	(14,253)	(13,901)
Net decrease in cash and cash equivalents	(279,117)	(137,927)
Cash and cash equivalents - beginning of period	723,109	550,401
Cash and cash equivalents - end of period	443,992	412,474
Supplemental disclosure of cash flow information:
Taxes paid during the period	5,914	14,959
Interest paid during the period	46,072	46,847
Investment affiliate
Adjustments to reconcile net income to cash provided by operating activities:
Loss (income) from investment affiliate	4,249	(5,542)
Cash flows used in investing activities
Investment in investment affiliates, net	$ (16,307)	$ (19,086)