Revenue - Disaggregation of Revenues By Performance Obligations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of revenue by performance obligation
Revenue	$ 858,938	$ 741,236	$ 2,451,273	$ 2,139,489
Management fee revenue - policy issuance and renewal services
Disaggregation of revenue by performance obligation
Revenue	649,049	551,666	1,840,478	1,584,213
Management fee revenue - policy issuance and renewal services | Transferred At Point in Time
Disaggregation of revenue by performance obligation
Revenue	649,049	551,666	1,840,478	1,584,213
Administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	203,269	183,310	591,387	536,101
Management fee revenue - administrative services
Disaggregation of revenue by performance obligation
Revenue	16,151	14,657	46,976	43,446
Management fee revenue - administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	16,151	14,657	46,976	43,446
Administrative services reimbursement revenue
Disaggregation of revenue by performance obligation
Revenue	187,118	168,653	544,411	492,655
Administrative services reimbursement revenue | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	$ 187,118	$ 168,653	$ 544,411	$ 492,655