Revenue - Disaggregation of Revenue by Performance Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of revenue by performance obligation
Revenue	$ 1,060,097	$ 990,438	$ 2,049,496	$ 1,871,139
Management fee revenue - policy issuance and renewal services
Disaggregation of revenue by performance obligation
Revenue	823,853	760,886	1,578,902	1,426,572
Management fee revenue - policy issuance and renewal services | Transferred At Point in Time
Disaggregation of revenue by performance obligation
Revenue	823,853	760,886	1,578,902	1,426,572
Administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	230,940	223,079	458,858	431,580
Management fee revenue - administrative services
Disaggregation of revenue by performance obligation
Revenue	18,296	17,051	35,941	33,985
Management fee revenue - administrative services | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	18,296	17,051	35,941	33,985
Administrative services reimbursement revenue
Disaggregation of revenue by performance obligation
Revenue	212,644	206,028	422,917	397,595
Administrative services reimbursement revenue | Transferred Over Time
Disaggregation of revenue by performance obligation
Revenue	$ 212,644	$ 206,028	$ 422,917	$ 397,595