SEC Schedule, Article 12-17, Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written premiums	$ (304,619)	$ (244,295)	$ (173,016)
Assumed	862,806	695,717	507,688
Net written premiums	$ 558,187	$ 451,422	$ 334,672
Percentage of Amount Assumed to Net	154.60%	154.10%	151.70%
Underwriting Division | Casualty
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written premiums	$ (184,364)	$ (138,912)	$ (85,393)
Assumed	550,666	431,817	277,455
Net written premiums	$ 366,302	$ 292,905	$ 192,062
Percentage of Amount Assumed to Net	150.30%	147.40%	144.50%
Underwriting Division | Professional Liability
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written premiums	$ (75,602)	$ (70,385)	$ (57,663)
Assumed	174,419	160,651	145,251
Net written premiums	$ 98,817	$ 90,266	$ 87,588
Percentage of Amount Assumed to Net	176.50%	178.00%	165.80%
Underwriting Division | Healthcare Liability
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written premiums	$ (39,117)	$ (34,590)	$ (29,960)
Assumed	116,290	101,619	84,982
Net written premiums	$ 77,173	$ 67,029	$ 55,022
Percentage of Amount Assumed to Net	150.70%	151.60%	154.50%
Underwriting Division | Baleen Specialty
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written premiums	$ (5,536)	$ (408)
Assumed	21,431	1,630
Net written premiums	$ 15,895	$ 1,222
Percentage of Amount Assumed to Net	134.80%	133.40%