Subsequent Events (Details) $ / shares in Units, $ in Millions		9 Months Ended
	Nov. 08, 2021 USD ($) $ / shares	Sep. 30, 2021 $ / shares	Dec. 31, 2020 $ / shares
Subsequent Event [Line Items]
Business combination converted exchange ratio		1.01547844
Common stock par value (in dollars per share) | $ / shares		$ 0.0001	$ 0.0001
Metromile, Inc. | Subsequent Event | Lemonade, Inc.
Subsequent Event [Line Items]
Fully diluted equity value | $	$ 500
Equity value, net of unrestricted cash and cash equivalents | $	$ 340
Business combination converted exchange ratio	0.05263
Common stock par value (in dollars per share) | $ / shares	$ 0.00001
Holding percentage of shares	11.30%