Noncontrolling Interests (Schedule of Redeemable Noncontrolling Interest) (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
Jun. 01, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Activity in redeemable noncontrolling interest
Beginning balance					$ 2,051,700
Net income attributable to redeemable noncontrolling interest		$ 62,057		$ 6,440	204,091	$ 90,822
Ending balance		2,779,033	$ 2,051,700		2,779,033
DaVinciRe Holdings Ltd.
Activity in redeemable noncontrolling interest
Beginning balance		1,431,101	1,085,985	1,082,425	1,034,946	1,011,659
Redemption of shares from redeemable noncontrolling interest, net of adjustments		1,018		(170)	86	(609)
Sale of shares to redeemable noncontrolling interests	$ 349,200	0		0	274,699	0
Net income attributable to redeemable noncontrolling interest		30,558		3,730	152,946	74,935
Ending balance		1,462,677	1,034,946	1,085,985	1,462,677	1,085,985
RenaissanceRe Medici Fund Ltd.
Activity in redeemable noncontrolling interest
Beginning balance		515,915	447,993	411,003	416,765	284,847
Redemption of shares from redeemable noncontrolling interest, net of adjustments		(7,008)		(8,720)	(44,448)	(52,223)
Sale of shares to redeemable noncontrolling interests		10,500		43,000	142,905	199,482
Net income attributable to redeemable noncontrolling interest		15,211		2,710	19,396	15,887
Ending balance		534,618	416,765	447,993	534,618	447,993
Vermeer Reinsurance Ltd.
Activity in redeemable noncontrolling interest
Beginning balance		765,450	0	0	599,989	0
Sale of shares to redeemable noncontrolling interests		0		0	150,000	0
Net income attributable to redeemable noncontrolling interest		16,288		0	31,749	0
Ending balance		$ 781,738	$ 599,989	$ 0	$ 781,738	$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Decrease in noncontrolling interest (for example, but not limited to, redeeming or purchasing the interests of noncontrolling shareholders, issuance of shares (interests) by the non-wholly owned subsidiary to the parent entity for other than cash, and a buyback of shares (interest) by the non-wholly owned subsidiary from the noncontrolling interests).

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Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.

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Amount of increase in noncontrolling interest from subsidiary issuance of equity interests to noncontrolling interest holders.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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