Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Variable Interest Entity [Line Items]
Contributions to subsidiaries			$ 0	$ 0
Assets	$ 12,544,763		12,544,763		$ 11,555,287
Liabilities	6,719,143		6,719,143		5,777,139
Ceded premiums written	239,212	$ 153,320	589,670	392,863
Ceded premiums earned	151,074	$ 110,150	287,249	218,894
Upsilon Reinsurance Fund Opportunities Ltd. | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Capital distribution payable	242,500		242,500
Return of capital to date			169,100		420,200
Assets	188,600		188,600		250,600
Liabilities	188,500		188,500		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]
Capital distribution payable	59,800		59,800
Return of capital to date			$ 47,100		$ 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			$ 100	600
Ceded premiums earned			3,600	3,600
Mona Lisa Re Ltd | DaVinci Reinsurance Ltd.
Variable Interest Entity [Line Items]
Ceded premiums written			100	500
Ceded premiums earned			2,500	$ 2,500
Mona Lisa Re Ltd | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	153,100		153,100		$ 184,000
Liabilities	$ 153,100		$ 153,100		$ 184,000