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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income (loss) available (attributable) to RenaissanceRe common shareholders	$ 33,773	$ 36,698	$ 367,854	$ 273,717	$ (83,906)	$ 32,681	$ 191,788	$ 56,713	$ 712,042	$ 197,276	$ (244,770)
Amount allocated to participating common shareholders									(8,545)	(2,121)	(457)
Net income (loss) allocated to RenaissanceRe common shareholders									$ 703,497	$ 195,155	$ (245,227)
Denominator:
Denominator for basic income (loss) per RenaissanceRe common share - weighted average common shares (in shares)	43,467	43,462	43,483	42,065	40,111	39,624	39,641	39,552	43,119	39,732	39,854
Per common share equivalents of employee stock options and performance shares (in shares)									56	23	0
Denominator for diluted income (loss) per RenaissanceRe common share - adjusted weighted average common shares and assumed conversions (in shares)	43,552	43,537	43,521	42,091	40,111	39,637	39,654	39,599	43,175	39,755	39,854
Net income (loss) available (attributable) to RenaissanceRe common shareholders per common share – basic (in usd per share)	$ 0.77	$ 0.83	$ 8.36	$ 6.43	$ (2.10)	$ 0.82	$ 4.78	$ 1.42	$ 16.32	$ 4.91	$ (6.15)
Net income (loss) available (attributable) to RenaissanceRe common shareholders per common share – diluted (in usd per share)	$ 0.77	$ 0.83	$ 8.35	$ 6.43	$ (2.10)	$ 0.82	$ 4.78	$ 1.42	$ 16.29	$ 4.91	$ (6.15)