Stock Incentive Compensation and Employee Benefit Plans (Equity Compensation Other than Options) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Number of shares:
Nonvested at Beginning of Period (in shares)	600,978	682,671	804,346
Awards granted (in shares)	229,509	258,233	243,701
Awards vested (in shares)	(348,611)	(332,933)	(358,219)
Awards forfeited (in shares)	(99)	(6,993)	(7,157)
Nonvested at End of Period (in shares)	481,777	600,978	682,671
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, at Beginning of Period (In dollars per share)	$ 76.24	$ 61.90	$ 53.91
Awards granted, Weighted average grant-dated fair value (In dollars per share)	$ 95.74	$ 87.82	$ 72.40
Awards vested, Weighted average grant-dated fair value (In dollars per share)	$ 73.79	$ 56.31	$ 51.26
Awards forfeited, Weighted average grant-dated fair value (In dollars per share)	$ 55.80	$ 58.14	$ 53.90
Nonvested, Weighted average grant-dated fair value, at End of Period (In dollars per share)	$ 87.36	$ 76.24	$ 61.90
Cash Settled Restricted Stock Unit (CSRSUs)
Number of shares:
Nonvested at Beginning of Period (in shares)	394,145	493,556	422,973
Awards granted (in shares)	119,382	149,760	225,105
Awards vested (in shares)	(159,094)	(176,265)	(128,401)
Awards forfeited (in shares)	(16,110)	(72,906)	(26,121)
Nonvested at End of Period (in shares)	338,323	394,145	493,556
Employee restricted stock
Number of shares:
Nonvested at Beginning of Period (in shares)	569,492	646,748	764,761
Awards granted (in shares)	215,054	241,071	226,827
Awards vested (in shares)	(332,725)	(311,334)	(337,683)
Awards forfeited (in shares)	(99)	(6,993)	(7,157)
Nonvested at End of Period (in shares)	451,722	569,492	646,748
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, at Beginning of Period (In dollars per share)	$ 76.11	$ 61.63	$ 53.68
Awards granted, Weighted average grant-dated fair value (In dollars per share)	$ 95.79	$ 87.85	$ 72.46
Awards vested, Weighted average grant-dated fair value (In dollars per share)	$ 73.74	$ 55.63	$ 51.06
Awards forfeited, Weighted average grant-dated fair value (In dollars per share)	$ 55.80	$ 58.14	$ 53.90
Nonvested, Weighted average grant-dated fair value, at End of Period (In dollars per share)	$ 87.29	$ 76.11	$ 61.63
Non-employee director restricted stock
Number of shares:
Nonvested at Beginning of Period (in shares)	31,486	35,923	39,585
Awards granted (in shares)	14,455	17,162	16,874
Awards vested (in shares)	(15,886)	(21,599)	(20,536)
Awards forfeited (in shares)	0	0	0
Nonvested at End of Period (in shares)	30,055	31,486	35,923
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, at Beginning of Period (In dollars per share)	$ 78.57	$ 66.83	$ 58.43
Awards granted, Weighted average grant-dated fair value (In dollars per share)	$ 95.06	$ 87.40	$ 71.69
Awards vested, Weighted average grant-dated fair value (In dollars per share)	$ 74.96	$ 66.06	$ 54.62
Awards forfeited, Weighted average grant-dated fair value (In dollars per share)	$ 0.00	$ 0.00	$ 0.00
Nonvested, Weighted average grant-dated fair value, at End of Period (In dollars per share)	$ 88.41	$ 78.57	$ 66.83
Performance Shares
Number of shares:
Nonvested at Beginning of Period (in shares)	359,543	359,520	289,867
Awards granted (in shares)	102,668	134,358	144,635
Awards vested (in shares)	0	(24,606)	(70,843)
Awards forfeited (in shares)	(213,639)	(109,729)	(4,139)
Nonvested at End of Period (in shares)	248,572	359,543	359,520
Weighted average grant-dated fair value:
Nonvested, Weighted average grant-dated fair value, at Beginning of Period (In dollars per share)	$ 30.55	$ 29.46	$ 30.06
Awards granted, Weighted average grant-dated fair value (In dollars per share)	$ 46.45	$ 33.46	$ 28.17
Nonvested, Weighted average grant-dated fair value, at End of Period (In dollars per share)	$ 39.62	$ 30.55	$ 29.46

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=rnr_CashSettledRestrictedStockUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=rnr_EmployeeRestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=rnr_NonEmployeeDirectorRestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: