Stockholders' Equity (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2022	Dec. 31, 2020	Apr. 04, 2025	Dec. 31, 2024
Sale of Stock [Line Items]
Common stock, authorized (in shares)	200,000,000				200,000,000
Common stock, par value (usd per share)	$ 0.00001				$ 0.00001
Common stock, issued (in shares)	74,665,921				72,720,866
Common stock, outstanding (in shares)	74,665,921				72,720,866
Preferred stock, authorized (in shares)	10,000,000				10,000,000
Preferred stock, par value (usd per share)	$ 0.00001				$ 0.00001
Preferred stock, issued (in shares)	0				0
Remaining unvested warrant shares (in shares)	3,170,834
Omnibus Agreement
Sale of Stock [Line Items]
Class of warrant common stock exercise price (usd per share)		$ 0.01
Vesting period		5 years
Omnibus Agreement | Warrant shares
Sale of Stock [Line Items]
Warrant, number of shares issuable, common stock (in shares)		3,352,025
Vesting period		5 years
Remaining unvested warrant shares (in shares)				3,170,834
Affiliated entity | The Lemonade Foundation | Lemonade, Inc.
Sale of Stock [Line Items]
Shares owned by foundation (in shares)	400,000				400,000
The Lemonade Foundation | Affiliated entity
Sale of Stock [Line Items]
Contribution to the lemonade foundation (in shares)	500,000		500,000