Revenue - Disaggregation of Revenue by Performance Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of revenue by performance obligation
Revenue	$ 1,089,796	$ 1,060,097	$ 2,101,707	$ 2,049,496
Management fee revenue - policy issuance and renewal services
Disaggregation of revenue by performance obligation
Revenue	862,879	823,853	1,649,278	1,578,902
Management fee revenue - policy issuance and renewal services | Transferred at Point in Time
Disaggregation of revenue by performance obligation
Revenue	862,879	823,853	1,649,278	1,578,902
Total revenue from administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	221,173	230,940	440,744	458,858
Management fee revenue - administrative services
Disaggregation of revenue by performance obligation
Revenue	19,619	18,296	39,094	35,941
Management fee revenue - administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	19,619	18,296	39,094	35,941
Administrative services reimbursement revenue
Disaggregation of revenue by performance obligation
Revenue	201,554	212,644	401,650	422,917
Administrative services reimbursement revenue | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	$ 201,554	$ 212,644	$ 401,650	$ 422,917