Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Variable Interest Entity [Line Items]
Contributions to subsidiaries			$ 0	$ 0
Assets	$ 12,659,531		12,659,531		$ 11,555,287
Liabilities	6,687,188		6,687,188		5,777,139
Ceded premiums written	146,002	$ 102,822	735,672	495,685
Ceded premiums earned	167,673	$ 120,609	454,922	339,503
Upsilon Reinsurance Fund Opportunities Ltd. | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Return of capital			242,500		420,200
Assets	215,400		215,400		250,600
Liabilities	215,400		215,400		250,500
Upsilon Reinsurance Fund Opportunities Ltd. | Variable Interest Entity, Primary Beneficiary | Non-Voting Preference Shares
Variable Interest Entity [Line Items]
Issuance of equity to third party investors			166,600		153,700
Contributions to subsidiaries			55,200		42,500
Upsilon Reinsurance Fund Opportunities Ltd. | Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd.
Variable Interest Entity [Line Items]
Return of capital			$ 59,800		$ 132,300
Variable interest entity, ownership percentage			28.90%		21.70%
Mona Lisa Re Ltd | Renaissance Reinsurance Ltd.
Variable Interest Entity [Line Items]
Ceded premiums written			$ 7,400	7,300
Ceded premiums earned			5,400	5,400
Mona Lisa Re Ltd | DaVinci Reinsurance Ltd.
Variable Interest Entity [Line Items]
Ceded premiums written			5,100	5,000
Ceded premiums earned			3,700	$ 3,700
Mona Lisa Re Ltd | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	187,500		187,500		$ 184,000
Liabilities	$ 187,500		$ 187,500		$ 184,000