Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows provided by operating activities
Net (loss) income	$ (354,671)	$ 630,048	$ 542,242
Adjustments to reconcile net (loss) income to net cash provided by operating activities
Amortization, accretion and depreciation	31,242	29,304	18,179
Equity in undistributed losses (earnings) of other ventures	6,295	5,504	(10,087)
Net realized and unrealized (gains) losses on investments	(135,822)	(141,328)	68,918
Net unrealized (gains) losses included in net investment income	(24,737)	(11,542)	13,549
Net unrealized losses included in other income	0	0	426
Change in:
Premiums receivable	(317,299)	(209,314)	(105,281)
Prepaid reinsurance premiums	(92,286)	(210,589)	(128,410)
Reinsurance recoverable	(1,307,066)	(145,038)	(64,104)
Deferred acquisition costs	(91,226)	(135,945)	(89,241)
Reserve for claims and claim expenses	2,232,114	81,249	(43,310)
Unearned premiums	246,036	342,471	144,040
Reinsurance balances payable	315,107	150,009	64,924
Other	538,100	99,943	13,140
Net cash provided by operating activities	1,045,787	484,772	424,985
Cash flows 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 sales (purchases) of equity investments trading	115,837	184,788	(147,558)
Net sales (purchases) 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
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)
Issuance of debt	295,866	0	445,589
Repayment of debt	(250,000)	0
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
Supplemental Cash Flow Information
Income taxes paid (refunded)	343	(1,118)	10,300
Interest paid	$ 44,171	$ 53,977	$ 40,755