v2.4.0.6

Fair Value Measurements (Company's Portfolio of Other Investments Measured Using Net Asset Valuations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Days
Fair Value	$ 709,615
Unfunded Commitments	105,235
Private equity partnerships [Member]
Fair Value	389,451
Unfunded Commitments	100,120
Senior secured bank loan funds [Member]
Fair Value	266,141
Unfunded Commitments	5,115
Non-U.S. fixed income funds [Member]
Fair Value	31,713
Unfunded Commitments	0
Redemption Frequency	Bi-monthly
Redemption Notice Period, Minimum	5
Redemption Notice Period, Maximum	20
Hedge funds [Member]
Fair Value	22,310
Unfunded Commitments	$ 0
Redemption Frequency	Annually, Bi-annually
Redemption Notice Period, Minimum	45
Redemption Notice Period, Maximum	90

X

- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period, Maximum

+ References

No definition available.

+ Details

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

X

- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period, Minimum

+ References

No definition available.

+ Details

Name:	rnr_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareInvestmentRedemptionNoticePeriodMinimum
Namespace Prefix:	rnr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

This element represents the total fair market value of investments in certain entities that calculate net asset value per share (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments). This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements, but may also be used in both the balance sheet and disclosure in the same submission. This item represents alternative investments as of the balance sheet date which may include investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds, and any other investment in which investee management calculates net asset value per share as the primary metric for investment value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19296-110258



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Subparagraph (a)

-Paragraph 6A

-URI http://asc.fasb.org/extlink&oid=6925170&loc=SL6742756-110258

+ Details

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

X

- Definition

States the frequency (for example, annually, semi-annually, quarterly) with which the entity can redeem its investment, or portion thereof, for each of those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments), by major category.

+ 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 (d)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=SL6742756-110258

+ Details

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

X

- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ 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 (c)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=SL6742756-110258

+ Details

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