Assets and Liabilities Held For Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Transfer of Financial Assets Accounted for as Sales [Line Items]
Total investments	$ 17,818,597	$ 17,368,789
Other assets	312,523	346,216
Total assets	27,465,519	26,330,094
Reserve for claims and claim expenses	9,406,707	9,384,349	$ 8,391,484
Other liabilities	351,320	932,024
Total liabilities	18,550,147	17,287,419
Disposal Group, Held-for-sale, Not Discontinued Operations | RenaissanceRe (UK) Limited
Transfer of Financial Assets Accounted for as Sales [Line Items]
Total investments	440,418	458,731
Other assets	24,165	40,284
Total assets	464,583	499,015
Reserve for claims and claim expenses	175,506	199,436
Other liabilities	2,863	925
Total liabilities	$ 178,369	$ 200,361