Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 23, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K/A
Document Annual Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	001-39484
Entity Registrant Name	METROMILE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	84-4916134
Entity Address, Address Line One	425 Market Street #700
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	888
Local Phone Number	242-5204
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		128,221,885
Documents Incorporated by Reference	None.
Entity Public Float			$ 809
Amendment Flag	false
Entity Central Index Key	0001819035
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	MILE
Security Exchange Name	NASDAQ
Warrant
Document Information [Line Items]
Title of 12(b) Security	Warrants, each whole warrant exercisable for one share of common stock at an exercise price of $11.50 per share
Trading Symbol	MILEW
Security Exchange Name	NASDAQ