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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income (loss) available (attributable) to RenaissanceRe common shareholders	$ (83,906)	$ 32,681	$ 191,788	$ 56,713	$ (3,452)	$ (504,812)	$ 171,142	$ 92,352	$ 197,276	$ (244,770)	$ 480,581
Amount allocated to participating common shareholders									(2,121)	(457)	(5,666)
Net income (loss) allocated to RenaissanceRe common shareholders									$ 195,155	$ (245,227)	$ 474,915
Denominator:
Denominator for basic income (loss) per RenaissanceRe common share - weighted average common shares (in shares)	40,111	39,624	39,641	39,552	39,478	39,591	39,937	40,408	39,732	39,854	41,314
Per common share equivalents of employee stock options and performance shares (in shares)									23	0	245
Denominator for diluted income (loss) per RenaissanceRe common share - adjusted weighted average common shares and assumed conversions (in shares)	40,111	39,637	39,654	39,599	39,478	39,591	40,024	40,623	39,755	39,854	41,559
Net income (loss) available (attributable) to RenaissanceRe common shareholders per common share – basic (in usd per share)	$ (2.10)	$ 0.82	$ 4.78	$ 1.42	$ (0.09)	$ (12.75)	$ 4.25	$ 2.26	$ 4.91	$ (6.15)	$ 11.50
Net income (loss) available (attributable) to RenaissanceRe common shareholders per common share – diluted (in usd per share)	$ (2.10)	$ 0.82	$ 4.78	$ 1.42	$ (0.09)	$ (12.75)	$ 4.24	$ 2.25	$ 4.91	$ (6.15)	$ 11.43