Noncontrolling Interests (Schedule Of Redeemable Noncontrolling Interest) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Activity in redeemable noncontrolling interest
Beginning balance			$ 1,175,594
Net (loss) income attributable to redeemable noncontrolling interest	$ (204,277)	$ 35,641	(132,338)	$ 110,867
Ending balance	1,033,729		1,033,729		$ 1,175,594
DaVinciRe Holdings Ltd.
Activity in redeemable noncontrolling interest
Beginning balance	1,019,918	953,443	994,458	930,955	930,955
Redemption of shares from redeemable noncontrolling interest	(12,068)	(400)	(78,870)	(92,204)
Sale of shares to redeemable noncontrolling interests	0	0	23,921	43,040
Net (loss) income attributable to redeemable noncontrolling interest	(195,508)	30,745	(127,167)	101,997
Ending balance	812,342	983,788	812,342	983,788	994,458
RenaissanceRe Medici Fund Ltd.
Activity in redeemable noncontrolling interest
Beginning balance	222,165	168,960	181,136	115,009	115,009
Redemption of shares from redeemable noncontrolling interest	(1,400)	(14,389)	(27,310)	(21,729)	(21,700)
Sale of shares to redeemable noncontrolling interests	9,391	21,298	72,732	78,615	79,500
Net (loss) income attributable to redeemable noncontrolling interest	(8,769)	4,896	(5,171)	8,870
Ending balance	$ 221,387	$ 180,765	$ 221,387	$ 180,765	$ 181,136