Revenue - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) obligation	Jun. 30, 2022 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Management fee rate as a percent of direct and affiliated assumed written premiums of the exchange			25.00%
Performance obligations under subscriber's agreement | obligation			2
Revenue recognized that was included in the contract liability at prior year-end | $	$ 10.5	$ 10.0	$ 23.8	$ 22.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation, satisfaction period	4 years		4 years