General - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Potentially dilutive securities (in shares)	0	0	0	0
Dividends declared and paid (in dollars per share)	$ 0.3175	$ 0.3175	$ 0.9525	$ 0.9525
Policy acquisition costs	$ 236,164,000	$ 230,293,000	$ 692,765,000	$ 630,016,000
Advertising expenses	11,500,000	6,500,000	24,400,000	13,800,000
Gain (loss) on sale of fixed assets			2,690,000	20,113,000
Ceded premiums earned	63,200,000	42,400,000	224,300,000	104,900,000
Losses and loss adjustment expenses, ceded	(28,000)	(1,500,000)	1,292,900,000	(2,500,000)
Revenue from contract with customer	7,700,000	6,400,000	21,600,000	18,000,000.0
Cost of goods and services sold	3,900,000	$ 3,200,000	11,100,000	9,600,000
Contract with customer, asset	0		0		$ 0
Contract with customer, liability	0		0		0
Revenue, remaining performance obligation	0		0		$ 0
Accrued interest receivable considered uncollectible or written off			0	0
Reinsurance Contract [Axis]: Catastrophe Participation Reinsurance Contract (the "Contract")
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Reinsurance reimbursable amount	30,000,000		$ 30,000,000
Reinsurance retention policy, threshold loss ratio			73.50%
Reinsurance Contract [Axis]: Catastrophe Reinsurance Treaty (the "Treaty")
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			$ 2,140,000,000
Reinsurance policy, amount retained			200,000,000
Reinsurance Contract [Axis]: Property Quota Share Reinsurance Contract ("Quota Share")
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Assumed maximum possible loss	32,000,000		32,000,000
Assumed premium written			11,000,000
Folsom, California Office Building | Disposal Group, Held-for-sale, Not Discontinued Operations
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Gain (loss) as a result of the held-for-sale classification				$ (5,400,000)
Folsom, California Office Building | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Sale price of fixed asset	$ 13,000,000.0		13,000,000.0
Gain (loss) on sale of fixed assets			$ 2,700,000