Revenue - Disaggregation of Revenue by Performance Obligation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of revenue by performance obligation
Revenue	$ 880,701	$ 752,465
Management fee revenue - policy issuance and renewal services
Disaggregation of revenue by performance obligation
Revenue	665,686	558,090
Management fee revenue - policy issuance and renewal services | Transferred At Point in Time
Disaggregation of revenue by performance obligation
Revenue	665,686	558,090
Administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	208,501	188,016
Management fee revenue - administrative services
Disaggregation of revenue by performance obligation
Revenue	16,934	15,189
Management fee revenue - administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	16,934	15,189
Administrative services reimbursement revenue
Disaggregation of revenue by performance obligation
Revenue	191,567	172,827
Administrative services reimbursement revenue | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	$ 191,567	$ 172,827