Earnings Per Share (Computation Of Basic And Diluted Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income available to RenaissanceRe common shareholders	$ 56,713	$ 92,352
Amount allocated to participating common shareholders	(546)	(907)
Net income allocated to RenaissanceRe common shareholders	$ 56,167	$ 91,445
Denominator:
Denominator for basic income per RenaissanceRe common share - weighted average common shares (in shares)	39,552	40,408
Per common share equivalents of employee stock options and restricted shares (in shares)	47	215
Denominator for diluted income per RenaissanceRe common share - adjusted weighted average common shares and assumed conversions (in shares)	39,599	40,623
Net income available to RenaissanceRe common shareholders per common share – basic (in dollars per share)	$ 1.42	$ 2.26
Net income available to RenaissanceRe common shareholders per common share – diluted (in dollars per share)	$ 1.42	$ 2.25