Condensed Consolidating Financial Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	$ (37,349)	$ 201,039
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	2,318,859	2,682,386
Purchases of fixed maturity investments trading	(2,312,461)	(3,007,124)
Net (purchases) sales of equity investments trading	137	13,747
Net (purchases) sales of short term investments	(594,641)	245,693
Net sales of other investments	(98,639)	36,402
Return of investment from investment in other ventures	0	20,000
Dividends and return of capital from subsidiaries	0	0
Contributions to subsidiaries	0	0
Due to (from) subsidiary	0	0
Net cash used in investing activities	(704,719)	(8,896)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	(13,224)	(13,027)
Dividends paid – preference shares	(5,595)	(5,595)
RenaissanceRe common share repurchases	0	(80,009)
Net third party redeemable noncontrolling interest share transactions	52,759	(51,166)
Taxes paid on withholding shares	(7,034)	(11,018)
Net cash provided by (used in) financing activities	26,906	(160,815)
Effect of exchange rate changes on foreign currency cash	1,543	1,602
Net (decrease) increase in cash and cash equivalents	(713,619)	32,930
Cash and cash equivalents, beginning of period	1,361,592	421,157
Cash and cash equivalents, end of period	647,973	454,087
Reportable Legal Entities | RenRe North America Holdings Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	659	(8,594)
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	42,793	12,473
Purchases of fixed maturity investments trading	(22,956)	(12,438)
Net (purchases) sales of equity investments trading	(21)	(74)
Net (purchases) sales of short term investments	(4,024)	(590)
Net sales of other investments	0	0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries	0	9,175
Contributions to subsidiaries	(16,500)	0
Due to (from) subsidiary	7	50
Net cash used in investing activities	(701)	8,596
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions	0	0
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	(42)	2
Cash and cash equivalents, beginning of period	139	162
Cash and cash equivalents, end of period	97	164
Reportable Legal Entities | Platinum Underwriters Finance, Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities		5,188
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading		36,397
Purchases of fixed maturity investments trading		(36,790)
Net (purchases) sales of equity investments trading		(2,181)
Net (purchases) sales of short term investments		(5,087)
Net sales of other investments		0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries		0
Contributions to subsidiaries		0
Due to (from) subsidiary		(34)
Net cash used in investing activities	0	(7,695)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions		0
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	0	(2,507)
Cash and cash equivalents, beginning of period		6,671
Cash and cash equivalents, end of period	0	4,164
Reportable Legal Entities | RenaissanceRe Finance, Inc. (Subsidiary Issuer)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	(23,449)	(17,914)
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	27,672	15,449
Purchases of fixed maturity investments trading	(12,698)	0
Net (purchases) sales of equity investments trading	0	0
Net (purchases) sales of short term investments	(5,925)	(3,374)
Net sales of other investments	0	0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries	0	9,175
Contributions to subsidiaries	0	(9,175)
Due to (from) subsidiary	14,106	2,522
Net cash used in investing activities	23,155	14,597
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions	0	0
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	(294)	(3,317)
Cash and cash equivalents, beginning of period	1,469	9,397
Cash and cash equivalents, end of period	1,175	6,080
Reportable Legal Entities | RenaissanceRe Holdings Ltd. (Parent Guarantor)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	(6,875)	(12,358)
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	119,542	38,449
Purchases of fixed maturity investments trading	(20,216)	(63,417)
Net (purchases) sales of equity investments trading	0	0
Net (purchases) sales of short term investments	54,728	269,585
Net sales of other investments	0	0
Return of investment from investment in other ventures		0
Dividends and return of capital from subsidiaries	177,250	65,180
Contributions to subsidiaries	(150,205)	(162,550)
Due to (from) subsidiary	(154,877)	(28,130)
Net cash used in investing activities	26,222	119,117
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	(13,224)	(13,027)
Dividends paid – preference shares	(5,595)	(5,595)
RenaissanceRe common share repurchases		(80,009)
Net third party redeemable noncontrolling interest share transactions	0	0
Taxes paid on withholding shares	(7,034)	(11,018)
Net cash provided by (used in) financing activities	(25,853)	(109,649)
Effect of exchange rate changes on foreign currency cash	0	0
Net (decrease) increase in cash and cash equivalents	(6,506)	(2,890)
Cash and cash equivalents, beginning of period	14,656	7,067
Cash and cash equivalents, end of period	8,150	4,177
Reportable Legal Entities | Other RenaissanceRe Holdings Ltd. Subsidiaries And Eliminations (Non-Guarantor Subsidiaries)
Cash flows (used in) provided by operating activities
Net cash (used in) provided by operating activities	(7,684)	234,717
Cash flows used in investing activities
Proceeds from sales and maturities of fixed maturity investments trading	2,128,852	2,579,618
Purchases of fixed maturity investments trading	(2,256,591)	(2,894,479)
Net (purchases) sales of equity investments trading	158	16,002
Net (purchases) sales of short term investments	(639,420)	(14,841)
Net sales of other investments	(98,639)	36,402
Return of investment from investment in other ventures		20,000
Dividends and return of capital from subsidiaries	(177,250)	(83,530)
Contributions to subsidiaries	166,705	171,725
Due to (from) subsidiary	140,764	25,592
Net cash used in investing activities	(753,395)	(143,511)
Cash flows provided by (used in) financing activities
Dividends paid – RenaissanceRe common shares	0	0
Dividends paid – preference shares	0	0
RenaissanceRe common share repurchases		0
Net third party redeemable noncontrolling interest share transactions	52,759	(51,166)
Taxes paid on withholding shares	0	0
Net cash provided by (used in) financing activities	52,759	(51,166)
Effect of exchange rate changes on foreign currency cash	1,543	1,602
Net (decrease) increase in cash and cash equivalents	(706,777)	41,642
Cash and cash equivalents, beginning of period	1,345,328	397,860
Cash and cash equivalents, end of period	$ 638,551	$ 439,502