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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross premiums written	$ 547,755	$ 625,677	$ 977,343	$ 1,159,652	$ 407,766	$ 640,269	$ 827,415	$ 922,090	$ 3,310,427	$ 2,797,540	$ 2,374,576
Net premiums written	411,094	453,255	604,509	663,044	288,223	483,221	555,745	544,136	2,131,902	1,871,325	1,535,312
Net premiums earned	574,613	531,849	429,385	440,282	421,473	547,792	382,265	366,045	1,976,129	1,717,575	1,403,430
Net claims and claim expenses incurred	477,638	410,510	60,167	171,703	304,064	1,221,696	142,587	193,081	1,120,018	1,861,428	530,831
Acquisition expenses	120,465	109,761	105,052	97,711	98,598	76,761	88,251	83,282	432,989	346,892	289,323
Operational expenses	58,859	40,593	37,543	41,272	29,192	42,537	41,766	47,283	178,267	160,778	197,749
Underwriting income (loss)									244,855	(651,523)	385,527
Net investment income	53,338	80,696	71,356	56,476	73,464	40,257	54,163	54,325	261,866	222,209	181,726
Net foreign exchange (losses) gains	(932)	(4,566)	(10,687)	3,757	(490)	(156)	3,109	8,165	(12,428)	10,628	(13,788)
Equity in earnings (losses) of other ventures	4,143	7,648	5,826	857	2,200	1,794	5,543	(1,507)	18,474	8,030	963
Other income	5,489	497	1,225	(1,242)	2,362	2,996	2,392	1,665	5,969	9,415	14,178
Net realized and unrealized (losses) gains on investments	(88,654)	13,630	(17,901)	(82,144)	(7,716)	42,052	58,113	43,373	(175,069)	135,822	141,328
Corporate expenses	(12,108)	(6,841)	(8,301)	(6,733)	(4,237)	(4,413)	(4,636)	(5,286)	(33,983)	(18,572)	(37,402)
Interest expense	(11,765)	(11,769)	(11,768)	(11,767)	(11,777)	(11,799)	(10,091)	(10,526)	(47,069)	(44,193)	(42,144)
Income (loss) before taxes	(132,838)	50,280	256,373	88,800	43,425	(722,471)	218,254	132,608	262,615	(328,184)	630,388
Income tax benefit (expense)	8,852	(1,451)	(4,506)	3,407	(41,226)	18,977	(3,904)	(334)	6,302	(26,487)	(340)
Net (income) loss attributable to redeemable noncontrolling interests	49,269	(6,440)	(54,483)	(29,899)	(56)	204,277	(37,612)	(34,327)	(41,553)	132,282	(127,086)
Dividends on preference shares	(9,189)	(9,708)	(5,596)	(5,595)	(5,595)	(5,595)	(5,596)	(5,595)	(30,088)	(22,381)	(22,381)
Net income (loss) available (attributable) to RenaissanceRe common shareholders	$ (83,906)	$ 32,681	$ 191,788	$ 56,713	$ (3,452)	$ (504,812)	$ 171,142	$ 92,352	197,276	(244,770)	480,581
Net claims and claim expenses incurred – current accident year									1,390,767	1,902,424	694,957
Net claims and claim expenses incurred – prior accident years									(270,749)	(40,996)	(164,126)
Total net incurred									$ 1,120,018	$ 1,861,428	$ 530,831
Net claims and claim expense ratio – current accident year									70.40%	110.80%	49.50%
Net claims and claim expense ratio – prior accident years									(13.70%)	(2.40%)	(11.70%)
Net claims and claim expense ratio – calendar year									56.70%	108.40%	37.80%
Underwriting expense ratio									30.90%	29.50%	34.70%
Combined ratio									87.60%	137.90%	72.50%
Other
Segment Reporting Information [Line Items]
Gross premiums written									$ 0	$ (7)	$ 0
Net premiums written									0	4	143
Net premiums earned									0	4	142
Net claims and claim expenses incurred									(197)	(1,583)	(1,110)
Acquisition expenses									(2)	(1)	0
Operational expenses									430	36	123
Underwriting income (loss)									(231)	1,552	1,129
Net investment income									261,866	222,209	181,726
Net foreign exchange (losses) gains									(12,428)	10,628	(13,788)
Equity in earnings (losses) of other ventures									18,474	8,030	963
Other income									5,969	9,415	14,178
Net realized and unrealized (losses) gains on investments									(175,069)	135,822	141,328
Corporate expenses									(33,983)	(18,572)	(37,402)
Interest expense									(47,069)	(44,193)	(42,144)
Income tax benefit (expense)									6,302	(26,487)	(340)
Net (income) loss attributable to redeemable noncontrolling interests									(41,553)	132,282	(127,086)
Dividends on preference shares									(30,088)	(22,381)	(22,381)
Net claims and claim expenses incurred – current accident year									0	0	0
Net claims and claim expenses incurred – prior accident years									(197)	(1,583)	(1,110)
Total net incurred									(197)	(1,583)	(1,110)
Property
Segment Reporting Information [Line Items]
Gross premiums written									1,760,926	1,440,437	1,111,263
Net claims and claim expenses incurred – prior accident years									(221,290)	(45,596)	(104,876)
Property | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written									1,760,926	1,440,437	1,111,263
Net premiums written									1,055,188	978,014	725,321
Net premiums earned									1,050,831	931,070	720,951
Net claims and claim expenses incurred									497,895	1,297,985	151,545
Acquisition expenses									177,912	113,816	97,594
Operational expenses									112,954	94,194	108,642
Underwriting income (loss)									262,070	(574,925)	363,170
Net claims and claim expenses incurred – current accident year									719,185	1,343,581	256,421
Net claims and claim expenses incurred – prior accident years									(221,290)	(45,596)	(104,876)
Total net incurred									$ 497,895	$ 1,297,985	$ 151,545
Net claims and claim expense ratio – current accident year									68.40%	144.30%	35.60%
Net claims and claim expense ratio – prior accident years									(21.00%)	(4.90%)	(14.60%)
Net claims and claim expense ratio – calendar year									47.40%	139.40%	21.00%
Underwriting expense ratio									27.70%	22.30%	28.60%
Combined ratio									75.10%	161.70%	49.60%
Casualty and Specialty
Segment Reporting Information [Line Items]
Gross premiums written									$ 1,549,501	$ 1,357,110	$ 1,263,313
Net claims and claim expenses incurred – prior accident years									(49,262)	6,183	(58,140)
Casualty and Specialty | Operating Segments
Segment Reporting Information [Line Items]
Gross premiums written									1,549,501	1,357,110	1,263,313
Net premiums written									1,076,714	893,307	809,848
Net premiums earned									925,298	786,501	682,337
Net claims and claim expenses incurred									622,320	565,026	380,396
Acquisition expenses									255,079	233,077	191,729
Operational expenses									64,883	66,548	88,984
Underwriting income (loss)									(16,984)	(78,150)	21,228
Net claims and claim expenses incurred – current accident year									671,582	558,843	438,536
Net claims and claim expenses incurred – prior accident years									(49,262)	6,183	(58,140)
Total net incurred									$ 622,320	$ 565,026	$ 380,396
Net claims and claim expense ratio – current accident year									72.60%	71.10%	64.30%
Net claims and claim expense ratio – prior accident years									(5.30%)	0.70%	(8.60%)
Net claims and claim expense ratio – calendar year									67.30%	71.80%	55.70%
Underwriting expense ratio									34.50%	38.10%	41.20%
Combined ratio									101.80%	109.90%	96.90%