Related Party Transactions (Details)	6 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($) director shares	Jun. 30, 2023 $ / shares	Dec. 31, 2020 shares	Dec. 31, 2024 USD ($) shares
Related Party Transaction [Line Items]
Due from related party (less than for December 31, 2024)	$ 40,300,000			$ 42,400,000
Outstanding amounts due (less than for December 31, 2024)	$ 124,200,000			105,700,000
The Lemonade Foundation | Affiliated entity
Related Party Transaction [Line Items]
Contribution to the Lemonade Foundation (in shares) | shares	500,000		500,000
Contribution of common stock to related party, fair value (usd per share) | $ / shares		$ 24.36
Due from related party (less than for December 31, 2024)	$ 0			100,000
Outstanding amounts due (less than for December 31, 2024)	$ 0			$ 100,000
The Lemonade Foundation | Affiliated entity | Lemonade, Inc.
Related Party Transaction [Line Items]
Shares owned by foundation (in shares) | shares	400,000			400,000
Related Party
Related Party Transaction [Line Items]
Number of shared directors | director	2