Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	$ 1,045,787	$ 484,772	$ 424,985
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	9,490,669	8,102,514	9,481,742
Purchases of fixed maturity investments trading	(10,093,532)	(8,282,720)	(9,683,068)
Proceeds from sales and maturities of fixed maturity investments available for sale	0	17,692	8,688
Net (purchases) sales of equity investments trading	115,837	184,788	(147,558)
Net (purchases) sales of short term investments	364,011	(118,617)	669,116
Net (purchases) sales of other investments	(19,419)	(68,589)	15,843
Net purchases of investments in other ventures	0	0	(10,150)
Net sales of other assets	0	400	4,500
Dividends and return of capital from subsidiaries	0	0	0
Contributions to subsidiaries	0	0	0
Due to (from) subsidiaries	0	0	0
Net purchase of Platinum	0	0	(678,152)
Net cash used in investing activities	(142,434)	(164,532)	(339,039)
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	(51,370)	(51,583)	(53,967)
Dividends paid – preference shares	(22,381)	(22,381)	(22,381)
RenaissanceRe common share repurchases	(188,591)	(309,434)	(259,874)
Issuance of debt	295,866	0	445,589
Repayment of debt	(250,000)	0		$ 0
Net repayment of debt				445,589
Net third party redeemable noncontrolling interest share transactions	260,475	(2,990)	(193,032)
Taxes paid on withholding shares	(15,139)	(14,943)	(10,248)
Net cash provided by (used in) financing activities	28,860	(401,331)	(93,913)
Effect of exchange rate changes on foreign currency cash	8,222	(4,637)	(10,732)
Net increase (decrease) in cash and cash equivalents	940,435	(85,728)	(18,699)
Cash and cash equivalents, beginning of period	421,157	506,885	525,584
Cash and cash equivalents, end of period	1,361,592	421,157	506,885
RenaissanceRe Holdings Ltd. (Parent Guarantor)
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	(4,109)	(3,509)	(28,965)
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	261,601	314,568	63,824
Purchases of fixed maturity investments trading	(344,463)	(336,345)	(161,183)
Net (purchases) sales of short term investments	243,571	(111,814)	(116,461)
Dividends and return of capital from subsidiaries	478,496	617,239	1,584,624
Net purchase of Platinum	0	0	(904,433)
Net cash used in investing activities	289,179	398,732	379,634
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	(51,370)	(51,583)	(53,967)
Dividends paid – preference shares	(22,381)	(22,381)	(22,381)
RenaissanceRe common share repurchases	(188,591)	(309,434)	(259,874)
Repayment of debt	0
Net repayment of debt				0
Taxes paid on withholding shares	(15,139)	(14,943)	(10,248)
Net cash provided by (used in) financing activities	(277,481)	(398,341)	(346,470)
Net increase (decrease) in cash and cash equivalents	7,589	(3,118)	4,199
Cash and cash equivalents, beginning of period	7,067	10,185	5,986
Cash and cash equivalents, end of period	14,656	7,067	10,185
Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Cash flows used in financing activities
Repayment of debt	0
Net repayment of debt				146,189
RenRe North America Holdings Inc. (Subsidiary Issuer)
Cash flows used in financing activities
Repayment of debt	0
Net repayment of debt				$ 0
Platinum Underwriters Finance, Inc. (Subsidiary Issuer)
Cash flows used in financing activities
Repayment of debt	(250,000)
RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Cash flows used in financing activities
Repayment of debt	0
Reportable Legal Entities | RenaissanceRe Holdings Ltd. (Parent Guarantor)
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	(4,109)	(3,509)	(28,965)
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	261,601	314,568	63,824
Purchases of fixed maturity investments trading	(344,463)	(336,345)	(161,183)
Proceeds from sales and maturities of fixed maturity investments available for sale		0	0
Net (purchases) sales of equity investments trading	0	0	0
Net (purchases) sales of short term investments	243,571	(111,814)	(116,461)
Net (purchases) sales of other investments	0	0	0
Net purchases of investments in other ventures		0	0
Net sales of other assets		0	0
Dividends and return of capital from subsidiaries	478,496	617,239	1,584,624
Contributions to subsidiaries	(669,672)	(108,674)	(294,733)
Due to (from) subsidiaries	319,646	23,758	207,996
Net purchase of Platinum			(904,433)
Net cash used in investing activities	289,179	398,732	379,634
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	(51,370)	(51,583)	(53,967)
Dividends paid – preference shares	(22,381)	(22,381)	(22,381)
RenaissanceRe common share repurchases	(188,591)	(309,434)	(259,874)
Issuance of debt	0
Net third party redeemable noncontrolling interest share transactions	0	0	0
Taxes paid on withholding shares	(15,139)	(14,943)	(10,248)
Net cash provided by (used in) financing activities	(277,481)	(398,341)	(346,470)
Effect of exchange rate changes on foreign currency cash	0	0	0
Net increase (decrease) in cash and cash equivalents	7,589	(3,118)	4,199
Cash and cash equivalents, beginning of period	7,067	10,185	5,986
Cash and cash equivalents, end of period	14,656	7,067	10,185
Reportable Legal Entities | Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	1,408,311	535,912	487,852
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	8,550,179	7,572,923	9,323,024
Purchases of fixed maturity investments trading	(9,229,732)	(7,532,276)	(9,462,845)
Proceeds from sales and maturities of fixed maturity investments available for sale		17,692	8,688
Net (purchases) sales of equity investments trading	32,265	(5,845)	87,993
Net (purchases) sales of short term investments	79,520	(41,586)	610,705
Net (purchases) sales of other investments	(19,419)	(68,589)	15,843
Net purchases of investments in other ventures		0	(10,150)
Net sales of other assets		400	4,500
Dividends and return of capital from subsidiaries	(529,537)	(633,264)	(1,917,177)
Contributions to subsidiaries	706,211	108,674	555,036
Due to (from) subsidiaries	(319,027)	(31,566)	93,809
Net purchase of Platinum			224,744
Net cash used in investing activities	(729,540)	(613,437)	(465,830)
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	0	0	0
Dividends paid – preference shares	0	0	0
RenaissanceRe common share repurchases	0	0	0
Issuance of debt	0
Net third party redeemable noncontrolling interest share transactions	260,475	(2,990)	(193,032)
Taxes paid on withholding shares	0	0	0
Net cash provided by (used in) financing activities	260,475	(2,990)	(46,843)
Effect of exchange rate changes on foreign currency cash	8,222	(4,637)	(10,732)
Net increase (decrease) in cash and cash equivalents	947,468	(85,152)	(35,553)
Cash and cash equivalents, beginning of period	397,860	483,012	518,565
Cash and cash equivalents, end of period	1,345,328	397,860	483,012
Reportable Legal Entities | RenRe North America Holdings Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	(8,253)	1,477	(9,201)
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	100,248	69,941	49,807
Purchases of fixed maturity investments trading	(99,568)	(123,046)	(59,040)
Proceeds from sales and maturities of fixed maturity investments available for sale		0	0
Net (purchases) sales of equity investments trading	(1,752)	(2,389)	33,693
Net (purchases) sales of short term investments	114	67,684	(63,305)
Net (purchases) sales of other investments	0	0	0
Net purchases of investments in other ventures		0	0
Net sales of other assets		0	0
Dividends and return of capital from subsidiaries	9,175	2,900	180,000
Contributions to subsidiaries	0	0	(8,550)
Due to (from) subsidiaries	13	(22,313)	(118,529)
Net purchase of Platinum			0
Net cash used in investing activities	8,230	(7,223)	14,076
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	0	0	0
Dividends paid – preference shares	0	0	0
RenaissanceRe common share repurchases	0	0	0
Issuance of debt	0
Net third party redeemable noncontrolling interest share transactions	0	0	0
Taxes paid on withholding shares	0	0	0
Net cash provided by (used in) financing activities	0	0	0
Effect of exchange rate changes on foreign currency cash	0	0	0
Net increase (decrease) in cash and cash equivalents	(23)	(5,746)	4,875
Cash and cash equivalents, beginning of period	162	5,908	1,033
Cash and cash equivalents, end of period	139	162	5,908
Reportable Legal Entities | Platinum Underwriters Finance, Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	(2,272)	(14,501)	(6,830)
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	289,741	145,082	45,087
Purchases of fixed maturity investments trading	(143,991)	(291,053)	0
Proceeds from sales and maturities of fixed maturity investments available for sale		0	0
Net (purchases) sales of equity investments trading	85,324	193,022	(269,244)
Net (purchases) sales of short term investments	41,299	(32,901)	238,177
Net (purchases) sales of other investments	0	0	0
Net purchases of investments in other ventures		0	0
Net sales of other assets		0	0
Dividends and return of capital from subsidiaries	0	0	65,000
Contributions to subsidiaries	(26,649)	0	(66,753)
Due to (from) subsidiaries	(123)	(81)	129
Net purchase of Platinum			1,537
Net cash used in investing activities	245,601	14,069	13,933
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	0	0	0
Dividends paid – preference shares	0	0	0
RenaissanceRe common share repurchases	0	0	0
Issuance of debt	0
Net repayment of debt			0
Net third party redeemable noncontrolling interest share transactions	0	0	0
Taxes paid on withholding shares	0	0	0
Net cash provided by (used in) financing activities	(250,000)	0	0
Effect of exchange rate changes on foreign currency cash	0	0	0
Net increase (decrease) in cash and cash equivalents	(6,671)	(432)	7,103
Cash and cash equivalents, beginning of period	6,671	7,103	0
Cash and cash equivalents, end of period	0	6,671	7,103
Reportable Legal Entities | RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash provided by operating activities	(347,890)	(34,607)	(17,871)
Cash flows provided by (used in) investing activities
Proceeds from sales and maturities of fixed maturity investments trading	288,900	0	0
Purchases of fixed maturity investments trading	(275,778)	0	0
Proceeds from sales and maturities of fixed maturity investments available for sale		0	0
Net (purchases) sales of equity investments trading	0	0	0
Net (purchases) sales of short term investments	(493)	0	0
Net (purchases) sales of other investments	0	0	0
Net purchases of investments in other ventures		0	0
Net sales of other assets		0	0
Dividends and return of capital from subsidiaries	41,866	13,125	87,553
Contributions to subsidiaries	(9,890)	0	(185,000)
Due to (from) subsidiaries	(509)	30,202	(183,405)
Net purchase of Platinum			0
Net cash used in investing activities	44,096	43,327	(280,852)
Cash flows used in financing activities
Dividends paid – RenaissanceRe common shares	0	0	0
Dividends paid – preference shares	0	0	0
RenaissanceRe common share repurchases	0	0	0
Issuance of debt	295,866
Net repayment of debt			299,400
Net third party redeemable noncontrolling interest share transactions	0	0	0
Taxes paid on withholding shares	0	0	0
Net cash provided by (used in) financing activities	295,866	0	299,400
Effect of exchange rate changes on foreign currency cash	0	0	0
Net increase (decrease) in cash and cash equivalents	(7,928)	8,720	677
Cash and cash equivalents, beginning of period	9,397	677	0
Cash and cash equivalents, end of period	$ 1,469	$ 9,397	$ 677