Segment Reporting (Schedule of Significant Components of the Company's Revenues and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Gross premiums written	$ 905,479	$ 861,068	$ 1,476,908	$ 1,564,295	$ 547,755	$ 625,677	$ 977,343	$ 1,159,652	$ 4,807,750	$ 3,310,427	$ 2,797,540
Net premiums written	725,367	704,130	1,022,965	929,031	411,094	453,255	604,509	663,044	3,381,493	2,131,902	1,871,325
Net premiums earned	970,125	906,748	911,502	550,028	574,613	531,849	429,385	440,282	3,338,403	1,976,129	1,717,575
Net claims and claim expenses incurred	762,093	654,520	453,373	227,035	477,638	410,510	60,167	171,703	2,097,021	1,120,018	1,861,428
Acquisition expenses	208,618	202,181	227,482	123,951	120,465	109,761	105,052	97,711	762,232	432,989	346,892
Operational expenses	64,571	53,415	59,814	44,933	58,859	40,593	37,543	41,272	222,733	178,267	160,778
Underwriting income (loss)									256,417	244,855	(651,523)
Net investment income	112,695	113,844	115,832	81,462	53,338	80,696	71,356	56,476	423,833	261,866	222,209
Net foreign exchange (losses) gains	(1,126)	(8,275)	9,309	(2,846)	(932)	(4,566)	(10,687)	3,757	(2,938)	(12,428)	10,628
Equity in earnings of other ventures	5,874	5,877	6,812	4,661	4,143	7,648	5,826	857	23,224	18,474	8,030
Other income	(160)	1,016	922	3,171	5,489	497	1,225	(1,242)	4,949	5,969	9,415
Net realized and unrealized gains (losses) on investments	17,897	31,938	194,003	170,645	(88,654)	13,630	(17,901)	(82,144)	414,483	(175,069)	135,822
Corporate expenses	(17,642)	(13,844)	(23,847)	(38,789)	(12,108)	(6,841)	(8,301)	(6,733)	(94,122)	(33,983)	(18,572)
Interest expense	(15,496)	(15,580)	(15,534)	(11,754)	(11,765)	(11,769)	(11,768)	(11,767)	(58,364)	(47,069)	(44,193)
Income (loss) before taxes	36,885	111,608	458,330	360,659	(132,838)	50,280	256,373	88,800	967,482	262,615	(328,184)
Income tax (expense) benefit	3,455	(3,664)	(9,475)	(7,531)	8,852	(1,451)	(4,506)	3,407	(17,215)	6,302	(26,487)
Net (income) loss attributable to redeemable noncontrolling interests	2,622	(62,057)	(71,812)	(70,222)	49,269	(6,440)	(54,483)	(29,899)	(201,469)	(41,553)	132,282
Dividends on preference shares	(9,189)	(9,189)	(9,189)	(9,189)	(9,189)	(9,708)	(5,596)	(5,595)	(36,756)	(30,088)	(22,381)
Net income (loss) available (attributable) to RenaissanceRe common shareholders	$ 33,773	$ 36,698	$ 367,854	$ 273,717	$ (83,906)	$ 32,681	$ 191,788	$ 56,713	712,042	197,276	(244,770)
Net claims and claim expenses incurred – current accident year									2,123,876	1,390,767	1,902,424
Net claims and claim expenses incurred – prior accident years									(26,855)	(270,749)	(40,996)
Total net incurred									$ 2,097,021	$ 1,120,018	$ 1,861,428
Net claims and claim expense ratio – current accident year									63.60%	70.40%	110.80%
Net claims and claim expense ratio – prior accident years									(0.80%)	(13.70%)	(2.40%)
Net claims and claim expense ratio – calendar year									62.80%	56.70%	108.40%
Underwriting expense ratio									29.50%	30.90%	29.50%
Combined ratio									92.30%	87.60%	137.90%
Other
Segment Reporting Information [Line Items]
Gross premiums written									$ 0	$ 0	$ (7)
Net premiums written									0	0	4
Net premiums earned									0	0	4
Net claims and claim expenses incurred									(40)	(197)	(1,583)
Acquisition expenses									(207)	(2)	(1)
Operational expenses									(828)	430	36
Underwriting income (loss)									1,075	(231)	1,552
Net investment income									423,833	261,866	222,209
Net foreign exchange (losses) gains									(2,938)	(12,428)	10,628
Equity in earnings of other ventures									23,224	18,474	8,030
Other income									4,949	5,969	9,415
Net realized and unrealized gains (losses) on investments									414,483	(175,069)	135,822
Corporate expenses									(94,122)	(33,983)	(18,572)
Interest expense									(58,364)	(47,069)	(44,193)
Income tax (expense) benefit									(17,215)	6,302	(26,487)
Net (income) loss attributable to redeemable noncontrolling interests									(201,469)	(41,553)	132,282
Dividends on preference shares									(36,756)	(30,088)	(22,381)
Net claims and claim expenses incurred – current accident year									0	0	0
Net claims and claim expenses incurred – prior accident years									(40)	(197)	(1,583)
Total net incurred									(40)	(197)	(1,583)
Property
Segment Reporting Information [Line Items]
Gross premiums written									2,430,985	1,760,926	1,440,437
Net claims and claim expenses incurred – prior accident years									(2,933)	(221,290)	(45,596)
Property | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written									2,430,985	1,760,926	1,440,437
Net premiums written									1,654,259	1,055,188	978,014
Net premiums earned									1,627,494	1,050,831	931,070
Net claims and claim expenses incurred									965,424	497,895	1,297,985
Acquisition expenses									313,761	177,912	113,816
Operational expenses									139,015	112,954	94,194
Underwriting income (loss)									209,294	262,070	(574,925)
Net claims and claim expenses incurred – current accident year									968,357	719,185	1,343,581
Net claims and claim expenses incurred – prior accident years									(2,933)	(221,290)	(45,596)
Total net incurred									$ 965,424	$ 497,895	$ 1,297,985
Net claims and claim expense ratio – current accident year									59.50%	68.40%	144.30%
Net claims and claim expense ratio – prior accident years									(0.20%)	(21.00%)	(4.90%)
Net claims and claim expense ratio – calendar year									59.30%	47.40%	139.40%
Underwriting expense ratio									27.80%	27.70%	22.30%
Combined ratio									87.10%	75.10%	161.70%
Casualty and Specialty
Segment Reporting Information [Line Items]
Gross premiums written									$ 2,376,765	$ 1,549,501	$ 1,357,110
Net claims and claim expenses incurred – prior accident years									(23,882)	(49,262)	6,183
Casualty and Specialty | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written									2,376,765	1,549,501	1,357,110
Net premiums written									1,727,234	1,076,714	893,307
Net premiums earned									1,710,909	925,298	786,501
Net claims and claim expenses incurred									1,131,637	622,320	565,026
Acquisition expenses									448,678	255,079	233,077
Operational expenses									84,546	64,883	66,548
Underwriting income (loss)									46,048	(16,984)	(78,150)
Net claims and claim expenses incurred – current accident year									1,155,519	671,582	558,843
Net claims and claim expenses incurred – prior accident years									(23,882)	(49,262)	6,183
Total net incurred									$ 1,131,637	$ 622,320	$ 565,026
Net claims and claim expense ratio – current accident year									67.50%	72.60%	71.10%
Net claims and claim expense ratio – prior accident years									(1.40%)	(5.30%)	0.70%
Net claims and claim expense ratio – calendar year									66.10%	67.30%	71.80%
Underwriting expense ratio									31.20%	34.50%	38.10%
Combined ratio									97.30%	101.80%	109.90%