Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Gross premiums written	$ 407,766	$ 640,269	$ 827,415	$ 922,090	$ 323,091	$ 430,224	$ 759,128	$ 862,133	$ 2,797,540	$ 2,374,576	$ 2,011,310
Net premiums written	288,223	483,221	555,745	544,136	219,499	284,222	519,916	511,675	1,871,325	1,535,312	1,416,183
(Increase) decrease in unearned premiums	133,250	64,571	(173,480)	(178,091)	132,402	62,299	(168,514)	(158,069)	(153,750)	(131,882)	(15,632)
Net premiums earned (Note 7)	421,473	547,792	382,265	366,045	351,901	346,521	351,402	353,606	1,717,575	1,403,430	1,400,551
Net investment income	73,464	40,257	54,163	54,325	47,316	51,423	54,124	28,863	222,209	181,726	152,567
Net foreign exchange gains (losses)	(490)	(156)	3,109	8,165	(5,420)	(5,986)	(690)	(1,692)	10,628	(13,788)	(3,051)
Equity in (losses) earnings of other ventures	2,200	1,794	5,543	(1,507)	4,960	(11,630)	6,022	1,611	8,030	963	20,481
Other income	2,362	2,996	2,392	1,665	5,177	2,268	2,654	4,079	9,415	14,178	13,472
Net realized and unrealized gains (losses) on investments	(7,716)	42,052	58,113	43,373	(49,967)	59,870	69,772	61,653	135,822	141,328	(68,918)
Total revenues	491,293	634,735	505,585	472,066	353,967	442,466	483,284	448,120	2,103,679	1,727,837	1,515,102
Expenses
Net claims and claim expenses incurred	304,064	1,221,696	142,587	193,081	123,901	112,575	167,750	126,605	1,861,428	530,831	448,238
Acquisition costs	98,598	76,761	88,251	83,282	74,146	80,580	69,005	65,592	346,892	289,323	238,592
Operational expenses	29,192	42,537	41,766	47,283	49,948	40,493	51,073	56,235	160,778	197,749	219,112
Corporate expenses	4,237	4,413	4,636	5,286	11,888	11,537	5,752	8,225	18,572	37,402	76,514
Interest expense	11,777	11,799	10,091	10,526	10,534	10,536	10,536	10,538	44,193	42,144	36,270
Total expenses	447,868	1,357,206	287,331	339,458	270,417	255,721	304,116	267,195	2,431,863	1,097,449	1,018,726
(Loss) income before taxes	43,425	(722,471)	218,254	132,608	83,550	186,745	179,168	180,925	(328,184)	630,388	496,376
Income tax (expense) benefit	(41,226)	18,977	(3,904)	(334)	7,700	1,316	(6,612)	(2,744)	(26,487)	(340)	45,866
Net (loss) income	2,199	(703,494)	214,350	132,274	91,250	188,061	172,556	178,181	(354,671)	630,048	542,242
Net (income) loss attributable to redeemable noncontrolling interests	(56)	204,277	(37,612)	(34,327)	(16,219)	(35,641)	(30,635)	(44,591)	132,282	(127,086)	(111,050)
Net (loss) income attributable to RenaissanceRe	2,143	(499,217)	176,738	97,947	75,031	152,420	141,921	133,590	(222,389)	502,962	431,192
Dividends on preference shares	(5,595)	(5,595)	(5,596)	(5,595)	(5,595)	(5,595)	(5,596)	(5,595)	(22,381)	(22,381)	(22,381)
Net (loss) income (attributable) available to RenaissanceRe common shareholders	$ (3,452)	$ (504,812)	$ 171,142	$ 92,352	$ 69,436	$ 146,825	$ 136,325	$ 127,995	$ (244,770)	$ 480,581	$ 408,811
Net (loss) income (attributable) available to RenaissanceRe common shareholders per common share – basic (in usd per share)	$ (0.09)	$ (12.75)	$ 4.25	$ 2.26	$ 1.70	$ 3.58	$ 3.23	$ 2.97	$ (6.15)	$ 11.50	$ 9.36
Net (loss) income (attributable) available to RenaissanceRe common shareholders per common share – diluted (in usd per share)	$ (0.09)	$ (12.75)	$ 4.24	$ 2.25	$ 1.69	$ 3.56	$ 3.22	$ 2.95	$ (6.15)	$ 11.43	$ 9.28
Average shares outstanding - basic	39,478	39,591	39,937	40,408	40,474	40,513	41,693	42,577	39,854	41,314	43,157
Average shares outstanding - diluted	39,478	39,591	40,024	40,623	40,707	40,733	41,885	42,912	39,854	41,559	43,526