Revenue - Disaggregation of Revenue by Performance Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of revenue by performance obligation
Revenue	$ 1,066,739	$ 999,886	$ 3,116,235	$ 2,871,025
Management fee revenue - policy issuance and renewal services
Disaggregation of revenue by performance obligation
Revenue	825,275	769,162	2,404,177	2,195,734
Management fee revenue - policy issuance and renewal services | Transferred at Point in Time
Disaggregation of revenue by performance obligation
Revenue	825,275	769,162	2,404,177	2,195,734
Total revenue from administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	234,525	223,908	693,383	655,488
Management fee revenue - administrative services
Disaggregation of revenue by performance obligation
Revenue	18,831	17,154	54,772	51,139
Management fee revenue - administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	18,831	17,154	54,772	51,139
Administrative services reimbursement revenue
Disaggregation of revenue by performance obligation
Revenue	215,694	206,754	638,611	604,349
Administrative services reimbursement revenue | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	$ 215,694	$ 206,754	$ 638,611	$ 604,349