Schedule II. Condensed Financial Information Of Registrant (Statements of Operations) (Details) - USD ($) $ 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
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 (losses) gains	(490)	(156)	3,109	8,165	(5,420)	(5,986)	(690)	(1,692)	10,628	(13,788)	(3,051)
Other (loss) 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
Interest expense	11,777	11,799	10,091	10,526	10,534	10,536	10,536	10,538	44,193	42,144	36,270
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
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 before equity in net (loss) income of subsidiaries									(328,184)	630,388	496,376
Equity in net (loss) income of subsidiaries									0	0	0
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
Parent Company
Revenues
Net investment income									23,109	24,178	15,391
Net foreign exchange (losses) gains									(1)	(2)	4
Other (loss) income									0	(772)	663
Net realized and unrealized gains (losses) on investments									(1,357)	4,151	(2,080)
Total revenues									21,751	27,555	13,978
Expenses
Interest expense									1,572	562	1,255
Operational expenses									11,314	13,716	4,249
Corporate expenses									18,546	26,848	40,808
Total expenses									31,432	41,126	46,312
Loss before equity in net (loss) income of subsidiaries									(9,681)	(13,571)	(32,334)
Equity in net (loss) income of subsidiaries									(212,708)	516,533	463,526
Net (loss) income attributable to RenaissanceRe									(222,389)	502,962	431,192
Dividends on preference shares									(22,381)	(22,381)	(22,381)
Net (loss) income (attributable) available to RenaissanceRe common shareholders									$ (244,770)	$ 480,581	$ 408,811