Acquisition of Platinum (Narrative) (Details) - USD ($)						12 Months Ended
	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Mar. 02, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 24, 2015
3.700% Senior Notes Due April 1, 2025
Business Acquisition [Line Items]
Senior notes interest rate						3.70%
Common Shares
Business Acquisition [Line Items]
Dividends per common share (in usd per share)	$ 0.32	$ 0.32	$ 0.32	$ 0.32
Platinum Underwriters Holdings, Ltd.
Business Acquisition [Line Items]
Dividends per common share (in usd per share)					$ 10
Dividends paid, value					$ 253,203,000
RenaissanceRe Finance, Inc. | 3.700% Senior Notes Due April 1, 2025
Business Acquisition [Line Items]
Debt instrument, face amount									$ 300,000,000
Senior notes interest rate									3.70%
Platinum Underwriters Holdings, Ltd.
Business Acquisition [Line Items]
Percent acquired					100.00%
Share price (in usd per share)					$ 76
Aggregate consideration transferred					$ 1,932,405,000
Cash consideration paid by RenaissanceRe to common shareholders of Platinum and holders of Platinum equity awards					1,160,000,000
Funds available to fund acquisition					604,400,000
Transaction-related costs						$ 300,000	$ 2,100,000	$ 53,500,000
Goodwill					191,729,000
Finite lived intangible assets acquired					$ 75,200,000
Weighted average useful life					8 years
Indefinite lived intangible assets acquired					$ 8,400,000
Adjustment to deferred tax asset					29,069,000
Other liabilities - deferred tax liability on identifiable intangible assets					$ (13,115,000)
Platinum Underwriters Holdings, Ltd. | Bridge Loan
Business Acquisition [Line Items]
Short-term debt									$ 300,000,000
Platinum Underwriters Holdings, Ltd. | Common Shares
Business Acquisition [Line Items]
Share price (in usd per share)					$ 35.96
Shares issued (in shares)					7,434,561
Shares issued, value					$ 761,819,000
Cash consideration paid by RenaissanceRe to common shareholders of Platinum and holders of Platinum equity awards					$ 904,433,000