Acquisition of Tokio Millennium Re (Schedule of Financial Results) (Details) - USD ($) $ 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
Business Acquisition [Line Items]
Total revenues	$ 1,105,305	$ 1,051,148	$ 1,238,380	$ 807,121	$ 547,997	$ 629,754	$ 479,204	$ 417,986	$ 4,201,954	$ 2,074,941	$ 2,103,679
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)
TMR
Business Acquisition [Line Items]
Total revenues									922,727
Net income (loss) available (attributable) to RenaissanceRe common shareholders									99,169
Corporate expenses associated with the acquisition									$ 49,700	$ 3,400