Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jan. 01, 2021 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of reportable segments | segment	1
Premium receivable, allowance for doubtful accounts	$ 2.7	$ 1.6
Amortization of net deferred acquisition costs	17.0	9.5	$ 4.9
Matching contributions	2.2	0.9	0.5
Advertising expenses	88.5	104.6	$ 58.3
Right-of-use assets	26.4	21.9
Lease, liabilities	$ 35.2	$ 22.3
Options to purchase common stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Requisite service period	4 years
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets				$ 16.9
Lease, liabilities				17.2
Deferred rent credit				$ 0.3
Internal use software
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful life	2 years