Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Related Party Transaction [Line Items]
Services and other revenues	$ 831,071	$ 803,918	$ 1,504,479	$ 1,464,501
Premiums ceded	2,448,518	2,901,140	4,388,494	4,809,079
Reinsurance recoverables	15,813,915		15,813,915		$ 14,616,279
Retroactive reinsurance transaction with Hagerty Re, net losses and loss adjustment expenses			(62,202)	0
Fronting
Related Party Transaction [Line Items]
Premiums ceded	2,105,099	2,257,573	3,600,730	3,610,787
Unconsolidated entities managed by Nephila [Member] \| Fund Management
Related Party Transaction [Line Items]
Services and other revenues	37,700	29,100	78,100	54,600
Nephila Reinsurers [Member]
Related Party Transaction [Line Items]
Reinsurance recoverables	241,900		241,900		496,000
Nephila Reinsurers [Member] \| Fronting
Related Party Transaction [Line Items]
Gross premiums volume	769,400	1,300,000	1,000,000	1,700,000
Premiums ceded	769,400	1,300,000	1,000,000	1,700,000
Nephila Reinsurers [Member] \| Industry Loss Warranties (ILW) Program
Related Party Transaction [Line Items]
Gross premiums volume	15,500	60,500	18,000	74,200
Premiums ceded	15,500	60,500	18,000	74,200
Hagerty, Inc. [Member]
Related Party Transaction [Line Items]
Gross premiums volume	344,836	304,106	598,137	524,033
Premiums ceded	330,186	$ 234,459	572,241	$ 404,144
Reinsurance recoverables	$ 342,200		342,200		317,100
Hagerty, Inc. [Member] \| Retroactive reinsurance transaction with Hagerty Re
Related Party Transaction [Line Items]
Retroactive reinsurance transaction with Hagerty Re, net losses and loss adjustment expenses			$ 62,200
Retroactive reinsurance transaction with Hagerty Re, unearned premiums					$ 92,500