Debt and Credit Facilities (Schedule of Credit Facilities) (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Line of Credit Facility [Line Items]
Credit facilities outstanding	$ 988,173
RenaissanceRe Revolving Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	0
Letter of Credit | Bank Of Montreal, Citibank Europe Plc and ING Bank N.V. | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	290,000
Letter of Credit | Secured Bilateral Facility | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	324,147
Letter of Credit | Unsecured Bilateral Facility | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	373,951
TMR | Letter of Credit | Line of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding	$ 75