Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows provided by (used in) operating activities
Net income	$ 467,857	$ 554,843	$ 595,148
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Share compensation expenses	38,341	33,073	27,630
(Gain) loss on sale of subsidiary	0	(709)	3,237
Amortization of discount on senior notes	108	108	108
Income from investment affiliate	(4,281)	(8,411)	(4,790)
Net realized (gains) losses on investments	(2,298)	(14,917)	764
Change in net unrealized losses on investments	32,395	2,842	52,419
Amortization of intangible assets	5,666	4,538	4,162
Loss (income) from operating affiliates	3,949	4,340	(542)
Foreign exchange losses included in net income	18,907	23,591	1,912
Amortization of premium on fixed maturities investments	23,075	19,107	19,093
Change in:
Premiums receivable	44,154	22,034	139,539
Deferred acquisition costs	(19,980)	(27,131)	14,255
Prepaid reinsurance premiums	4,955	34,443	(4,695)
Loss reserves recoverable	24,659	81,824	69,910
Paid losses recoverable	15,111	43,580	(33,807)
Income taxes recoverable	(16,477)	0	0
Deferred tax asset	1,979	0	0
Accrued investment income	878	2,417	2,499
Other assets	10,023	31,264	(75,623)
Reserve for losses and loss expenses	(231,345)	(404,280)	(491,380)
Unearned premiums	(23,019)	18,161	(81,454)
Reinsurance balances payable	(52,785)	(32,262)	(1,580)
Deferred tax liability	(1,820)	(45,380)	(1,008)
Accounts payable and accrued expenses	(5,546)	(2,914)	(431)
Net cash provided by operating activities	334,506	340,161	235,366
Cash flows provided by (used in) investing activities
Proceeds on sales of fixed maturity investments	3,842,408	4,756,555	4,370,548
Proceeds on maturities of investments	332,410	554,619	490,459
Purchases of fixed maturities	(4,225,031)	(4,391,814)	(5,392,728)
(Purchases) sales of short-term investments, net	(436,690)	(329,301)	934,759
(Purchases) sales of other investments, net	(5,988)	(143,597)	26,508
(Increase) decrease in securities lending collateral	(4,393)	2,922	(3,167)
Redemption from operating affiliates	46,603	0	0
Decrease (increase) in restricted cash	99,733	27,489	(172,962)
Proceeds on sale of subsidiary, net of cash	0	16,459	21,388
Purchase of subsidiary, net of cash acquired	0	(643,545)	0
Net cash (used in) provided by investing activities	(370,834)	(162,681)	253,813
Cash flows provided by (used in) financing activities
Net proceeds on issuance of notes payable to AlphaCat investors	75,493	0	0
Issuance of common shares, net	17,407	5,347	1,211
Purchases of common shares under share repurchase program	(260,430)	(510,952)	(513,504)
Dividends paid	(112,991)	(117,043)	(360,071)
Increase (decrease) in securities lending payable	4,393	(2,922)	3,167
Third party investment in redeemable noncontrolling interest	499,200	300,200	142,190
Third party redemption of redeemable noncontrolling interest	(86,934)	(13,192)	0
Third party investment in noncontrolling interest	9,600	117,243	136,619
Third party distributions of noncontrolling interest	(168,733)	(237,183)	(289,260)
Third party subscriptions received on AlphaCat Funds and Sidecars	249,636	127,400	15,600
Net cash provided by (used in) financing activities	226,641	(331,102)	(864,048)
Effect of foreign currency rate changes on cash and cash equivalents	(17,605)	(25,310)	(6,364)
Net increase (decrease) in cash	172,708	(178,932)	(381,233)
Cash and cash equivalents - beginning of year	550,401	729,333	1,110,566
Cash and cash equivalents - end of year	723,109	550,401	729,333
Taxes paid during the year	16,050	42,689	5,407
Interest paid during the year	55,047	54,526	52,191
Operating Affiliates
Cash flows provided by (used in) investing activities
Investments in affiliates	0	0	(6,500)
Investment Affiliates
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Income from investment affiliate	(4,281)	(8,411)
Cash flows provided by (used in) investing activities
Investments in affiliates	$ (19,886)	$ (12,468)	$ (14,492)