Schedule II. Condensed Financial Information Of Registrant (Statements of Cash Flows) (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
Cash flows (used in) provided by operating activities
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
Less: equity in net loss (income) of subsidiaries									0	0	0
Adjustments to reconcile net (loss) income to net cash provided by operating activities
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
Other									538,100	99,943	13,140
Net cash provided by operating activities									1,045,787	484,772	424,985
Cash flows provided by (used in) investing activities
Proceeds from maturities and sales 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)
Net (purchases) sales of short term investments									364,011	(118,617)	669,116
Dividends and return of capital 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 provided by (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)
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)
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	421,157	506,885	525,584
Cash and cash equivalents, end of period	1,361,592				421,157				1,361,592	421,157	506,885
Parent Company
Cash flows (used in) provided by operating activities
Net (loss) income attributable to RenaissanceRe									(222,389)	502,962	431,192
Less: equity in net loss (income) of subsidiaries									212,708	(516,533)	(463,526)
Loss before equity in net income of subsidiaries									(9,681)	(13,571)	(32,334)
Adjustments to reconcile net (loss) income to net cash provided by operating activities
Net realized and unrealized (gains) losses on investments									1,357	(4,151)	2,080
Other									4,215	14,213	1,289
Net cash provided by operating activities									(4,109)	(3,509)	(28,965)
Cash flows provided by (used in) investing activities
Proceeds from maturities and sales 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
Contributions to subsidiaries									(669,672)	(108,674)	(294,733)
Due to (from) subsidiary									319,646	23,758	207,996
Net purchase of Platinum									0	0	(904,433)
Net cash used in investing activities									289,179	398,732	379,634
Cash flows provided by (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)
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	7,067	10,185	5,986
Cash and cash equivalents, end of period	$ 14,656				$ 7,067				$ 14,656	$ 7,067	$ 10,185