CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (241.3)	$ (122.3)	$ (108.5)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	3.7	1.7	0.6
Stock-based compensation	44.1	10.6	4.3
Amortization of discount on bonds	(4.2)	(0.4)	(0.5)
Provision for bad debt	6.2	2.2	0.9
Common shares contribution to Lemonade Foundation	0.0	12.2	0.0
Unrealized loss on money market funds	0.0	0.1	0.0
Changes in operating assets and liabilities:
Premium receivable	(47.2)	(34.2)	(29.1)
Reinsurance recoverable	(40.8)	(28.7)	(8.5)
Prepaid reinsurance premium	(58.3)	(90.3)	0.5
Deferred acquisition costs	(2.7)	(1.7)	(1.2)
Other assets	(38.6)	(12.0)	(1.1)
Unpaid losses and loss adjustment expenses	51.6	18.1	15.1
Unearned premium	83.9	55.8	40.3
Trade payables	(0.4)	0.7	(0.8)
Funds held for reinsurance treaties	41.0	62.1	0.0
Deferred ceding commission	14.1	22.4	0.0
Ceded premium payable	5.7	9.1	0.0
Other liabilities and accrued expenses	38.6	2.9	9.9
Net cash used in operating activities	(144.6)	(91.7)	(78.1)
Cash flows from investing activities:
Proceeds from short-term investments sold or matured	20.2	70.0	21.0
Proceeds from bonds sold or matured	27.2	2.3	1.0
Cost of short-term investments acquired	(130.8)	(14.9)	(69.2)
Cost of bonds acquired	(712.0)	(2.9)	(3.5)
Purchases of property and equipment	(9.4)	(4.4)	(2.7)
Purchases of intangible assets	0.0	0.0	(0.6)
Net cash (used in) provided by investing activities	(804.8)	50.1	(54.0)
Cash flows from financing activities:
Proceeds from Initial Public Offering and Follow-on Offering, net of underwriting discounts and commissions and offering costs	640.3	338.0	0.0
Proceeds from release of shares upon repayment	0.0	1.3	0.0
Issuance of Preferred stock, net	0.0	0.0	299.4
Proceeds from stock exercises	9.3	1.8	0.7
Net cash provided by financing activities	649.6	341.1	300.1
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1.0)	1.6	(0.1)
Net (decrease) increase in cash, cash equivalents and restricted cash	(300.8)	301.1	167.9
Cash, cash equivalents and restricted cash at beginning of year	571.4	270.3	102.4
Cash, cash equivalents and restricted cash at end of year	270.6	571.4	270.3
Supplemental disclosure of cash flow information:
Cash paid for income taxes	$ 3.2	$ 1.6	$ 0.5