Summary of Significant Accounting Policies - Investment in Unconsolidated Investees (Details)	12 Months Ended
	Dec. 31, 2024 USD ($) item	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
INVESTMENT IN UNCONSOLIDATED INVESTEES:
Investment in unconsolidated investees	$ 56,477,000	$ 56,966,000
Investee earnings recorded in income	(4,869,000)	9,610,000	$ 9,853,000
Reinsurance assumed	27,002,000	22,798,000	33,830,000
Net premiums earned	1,526,406,000	1,294,306,000	1,144,436,000
Undistributed earnings from equity method investees included in retained earnings	$ 54,000,000
Dividends received from investments in unconsolidated investees		0	0
Prime Holdings Insurance Services, Inc. (Prime)
INVESTMENT IN UNCONSOLIDATED INVESTEES:
Equity ownership interest (as a percent)	23.00%
Investment in unconsolidated investees	$ 56,000,000
Investee earnings recorded in income	$ 5,000,000	10,000,000	13,000,000
Number of insurance carriers Company writes through | item	2
Reinsurance assumed	$ 9,000,000	7,000,000	21,000,000
Net premiums earned	8,000,000	13,000,000	23,000,000
Dividends received from investments in unconsolidated investees	$ 3,000,000	$ 0	$ 0