Noncontrolling Interests (Summary of Redeemable Noncontrolling Interest) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests	$ 3,071,308	$ 2,051,700
Net income attributable to redeemable noncontrolling interests	201,469	41,553	$ (132,282)
DaVinciRe Holdings Ltd.
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests	1,435,581	1,034,946	1,011,659
Net income attributable to redeemable noncontrolling interests	127,084	27,638	(134,860)
RenaissanceRe Medici Fund Ltd.
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests	632,112	416,765	284,847
Net income attributable to redeemable noncontrolling interests	25,759	13,926	2,578
Vermeer Reinsurance Ltd.
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests	1,003,615	599,989	0
Net income attributable to redeemable noncontrolling interests	$ 48,626	$ (11)	$ 0