This item represents the weighted average effective yield percentage of debt securities.

No definition available.

Name:	rnr_DebtSecuritiesWeightedAverageEffectiveYield
Namespace Prefix:	rnr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the weighted average life in years of debt securities.

+ References

No definition available.

+ Details

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Namespace Prefix:	rnr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents senior secured bank loan funds in a closed end fund, which the Company has no right to redeem.

+ References

No definition available.

+ Details

Name:	rnr_InvestmentInClosedEndFund
Namespace Prefix:	rnr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of investment in certain entities that calculate net asset value per share. Includes, but is not limited to, by unit, membership interest, or other ownership interest. Investment includes, but is not limited to, investment in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds. Excludes measurement of net asset value as estimate of fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a recurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueDisclosureRecurring
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

- Definition

Estimate remaining period the underlying assets are expected to be liquidated by the investees for investments for which net asset value per share is calculated (including by unit, membership interest, or other ownership interest unit measure), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregation of the liabilities reported on the balance sheet measured at fair value on a recurring basis by the entity.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of other liabilities.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherLiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

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

Fair Value Measurements (Narrative) (Details) - USD ($)	3 Months Ended
Fair Value Measurements (Narrative) (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other liabilities	$ 5,313,000		$ 5,494,000
Debt	989,995,000		989,623,000
Long-term debt, fair value	993,900,000		$ 1,000,000,000
Net unrealized gains recognized in earnings	1,465,000	$ 6,863,000
Investment balance	216,118,000
Other Investments \| Net investment income
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized gains recognized in earnings	1,500,000	6,900,000
Other assets and (liabilities) \| Other income (loss)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized gains recognized in earnings	0	$ 0
Significant Unobservable Inputs (Level 3) \| Internal valuation model \| Assumed reinsurance contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value	893,000
Significant Unobservable Inputs (Level 3) \| Internal valuation model \| Assumed and ceded (re)insurance contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, fair value	$ 3,673,000
U.S. treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.30%		1.90%
Agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.40%		2.10%
Municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.50%		2.20%
Non-U.S. government (Sovereign debt)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.40%		2.00%
Non-U.S. government-backed corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	2.70%		2.30%
Corporate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	4.20%		3.80%
Agency mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.30%		3.00%
Weighted average life	7 years 3 months 18 days	6 years 4 months 24 days
Non-agency prime residential mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.90%		3.70%
Weighted average life	5 years 3 months 18 days	5 years 1 month 6 days
Alt-A non-agency mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.80%		3.70%
Weighted average life	6 years 2 months 12 days	6 years 2 months 12 days
Commercial mortgage-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.30%		2.90%
Weighted average life	4 years 8 months	4 years 6 months
Asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	3.50%		2.80%
Weighted average life	3 years 2 months	3 years
Short term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	1.70%		1.40%
Private equity partnerships
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment balance	$ 190,067,000
Private equity partnerships \| Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	7 years
Private equity partnerships \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	10 years
Senior secured bank loan funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in closed end fund	$ 13,800,000
Investment balance	$ 13,771,000
Senior secured bank loan funds \| Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	4 years
Senior secured bank loan funds \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liquidation period for fund assets	5 years
Hedge funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment balance	$ 12,280,000
Hedge funds redeemable at option of shareholder
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment balance	11,800,000
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	989,995,000		$ 989,623,000
Long-term debt, fair value	$ 993,879,000		$ 1,018,235,000