CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (297.7)	$ (521.1)	$ (363.0)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	30.5	19.3	3.7
Warrant compensation expense	14.5	8.8	0.0
Tender offer	0.0	0.0	25.1
Depreciation and amortization	13.8	16.6	15.6
Bad debt expense	17.4	20.9	23.6
Loss on early extinguishment of debt	0.0	15.9	0.0
Warrants fair value adjustment	0.0	0.0	54.7
Paid-in-kind interest expense	0.0	10.6	9.1
Paid-in-kind interest paid	0.0	(20.5)	0.0
Net realized gains on investments	(0.5)	(2.4)	(0.3)
Gain on lease modification	(0.9)	0.0	0.0
Change in fair value of equity securities	0.0	(3.8)	0.0
Changes in operating assets and liabilities:
Premiums receivable	18.8	(39.7)	(31.0)
Reinsurance recoverable	6.2	(30.4)	(99.5)
Prepaid reinsurance premiums	26.6	12.0	(95.4)
Other assets	(7.5)	0.8	(21.7)
Losses and loss adjustment expenses reserves	(32.8)	83.0	96.5
Unearned premiums	(43.6)	23.0	11.7
Reinsurance premiums payable	18.2	12.5	63.4
Accounts payable and accrued expenses	17.9	(19.2)	18.2
Other liabilities	8.5	10.3	2.1
Net cash used in operating activities	(210.6)	(403.4)	(287.2)
Cash flows from investing activities:
Purchases of investments	(47.7)	(17.0)	(158.4)
Proceeds from maturities, call and pay downs of investments	34.1	34.7	42.5
Sales of investments	7.1	70.4	17.9
Purchases of indefinite-lived intangible assets and transaction costs	(1.3)	0.0	(8.9)
Capitalization of internally developed software	(8.8)	(6.6)	(5.4)
Purchases of fixed assets	0.0	(4.6)	(1.8)
Net cash (used in) provided by investing activities	(16.6)	76.9	(114.1)
Cash flows from financing activities:
Proceeds from exercise of stock options and restricted stock units, net of tax proceeds/(withholding)	0.3	3.2	2.1
Proceeds from issuance of common stock from IPO and concurrent private placements, net of issuance costs	0.0	0.0	1,098.1
Proceeds from issuance of preferred stock and related warrants	0.0	126.5	0.0
Payment of preferred stock and related warrants issuance costs	(3.0)	(10.5)	0.0
Proceeds from issuance of debt and related warrants, net of issuance costs	286.0	0.0	12.0
Repayments of long-term debt	0.0	(199.5)	(13.5)
Purchases of treasury stock	0.0	0.0	(0.2)
Net cash provided by (used in) financing activities	283.3	(80.3)	1,098.5
Net increase (decrease) in cash, cash equivalents and restricted cash	56.1	(406.8)	697.2
Cash, cash equivalents and restricted cash at beginning of year	707.0	1,113.8	416.6
Cash, cash equivalents and restricted cash at end of year	$ 763.1	$ 707.0	$ 1,113.8