Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959

+ Details

Name:	us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_GainLossOnInvestmentsMember1
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CreditDefaultSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_TotalReturnSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EquityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_ForeignCurrencyGainLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=rnr_ForeignCurrencyForwardContractsUnderwritingAndNonInvestmentOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=rnr_ForeignCurrencyForwardContractsInvestmentOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Derivative Instruments (Gain (Loss) Recognized in the Consolidated Statements of Operations Related to its Derivative Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	$ 1,841	$ 9,397	$ 66,909	$ 51,755
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	3,798	6,133	66,716	47,647
Not Designated as Hedging Instrument \| Net realized and unrealized gains on investments \| Interest rate futures
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	4,985	7,263	95,548	35,570
Not Designated as Hedging Instrument \| Net realized and unrealized gains on investments \| Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	243	887	2,852	2,071
Not Designated as Hedging Instrument \| Net realized and unrealized gains on investments \| Credit default swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(87)	65	(3,010)	5,521
Not Designated as Hedging Instrument \| Net realized and unrealized gains on investments \| Total return swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	1,227	1,960	(5,759)	6,995
Not Designated as Hedging Instrument \| Net realized and unrealized gains on investments \| Equity futures
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(4,335)	959	(30,045)	11,946
Not Designated as Hedging Instrument \| Net foreign exchange gains (losses) \| Foreign currency forward contracts, underwriting and non-investment operations
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	2,495	(5,912)	9,073	(13,086)
Not Designated as Hedging Instrument \| Net foreign exchange gains (losses) \| Foreign currency forward contracts, investment operations
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(730)	911	(1,943)	(1,370)
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized on derivatives	(1,957)	3,264	193	4,108
Designated as Hedging Instrument \| Foreign currency forward contracts, investment operations
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive loss	$ (1,957)	$ 3,264	$ 193	$ 4,108