Overview and Basis of Presentation (Policies)	3 Months Ended
Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim unaudited consolidated financial statements have been prepared in accordance GAAP and in accordance with the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). References to the Accounting Standard Codification (“ASC”) and Accounting Standard Updates (“ASU”) included hereinafter refer to the Accounting Standards Codification and Updates established by the Financial Accounting Standards Board (“FASB”) as the source of authoritative GAAP. The consolidated financial statements include the accounts of Metromile, Inc. and its subsidiaries, all of which are wholly owned. All intercompany accounts and transactions have been eliminated in consolidation. These unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 ("the Company’s 2021 Annual Report").
Reclassifications	Reclassifications Reclassifications have been made to the prior year balances to conform to the current year presentation. In particular, accounts receivable, and digital assets, net have been combined with prepaid expenses and other assets into a single line on the consolidated balance sheets and consolidated statements of cash flows. The reclassifications had no effect on stockholders’ deficit or net loss after taxes as previously reported.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes. On an ongoing basis, the Company’s management evaluates estimates, including those related to contingent assets and liabilities as of the date of the financial statements as well as the reported amounts of revenue and expense during the reporting period. The Company’s principal estimates include: unpaid losses and LAE reserves; the fair value of investments; the fair value of stock-based awards; the fair value of the warrant liability; premium refunds to policyholders; reinsurance recoverable on unpaid loss; and the valuation allowance for income taxes. Because of uncertainties associated with estimating the amounts, timing and likelihood of possible outcomes, actual results could differ materially from these estimates.
Discontinued Operations and Held for Sale	Discontinued Operations and Held for Sale A business is classified as held for sale when management having the authority to approve the action commits to a plan to sell the business, the sale is probable to occur during the next 12 months at a price that is reasonable in relation to its current fair value and certain other criteria are met. A business classified as held for sale is recorded at the lower of its carrying amount or estimated fair value less cost to sell. When the carrying amount of the business exceeds its estimated fair value less cost to sell, a loss is recognized and updated each reporting period as appropriate. The results of operations of business classified as held for sale are reported as discontinued operations if the disposal represents a strategic shift that will have a major effect on the entity’s operations and financial results.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Reference Rate Reform In March 2020, FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides optional expedients and exceptions to contract modifications and hedging relationships that reference LIBOR or another reference rate expected to be discontinued. The standard is effective upon issuance through December 31, 2022 and may be applied at the beginning of the interim period that includes March 12, 2020 or any date thereafter. The Company is currently evaluating this new standard and the impact it will have on its consolidated financial statements. This standard may be elected and applied prospectively over time from March, 2020 through December 31, 2022 as reference rate reform activities occur. The Company is evaluating the method of adoption and impact of the standard on its consolidated financial statements and related disclosures. Government Assistance In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance. This update requires annual disclosures about transactions with a government that are accounted for by applying a grant or contribution accounting model by analogy. This standard is effective for annual periods beginning after December 15, 2021. Early adoption is permitted. The amendments should be applied either (1) prospectively to all transactions within the scope of the amendments that are reflected in financial statements at the date of initial application and new transactions that are entered into after the date of initial application or (2) retrospectively to those transactions. The Company is currently evaluating the impact of these amendments on its consolidated financial statements.
Fair Value Measurement	Topic 820, Fair Value Measurements, defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Topic 820 also establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value: Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. An asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques used need to maximize the use of observable inputs and minimize the use of unobservable inputs. The following is a description of the valuation methodologies used for instruments measured at fair value on a recurring basis and recognized in the accompanying Consolidated Balance Sheet, as well as the general classification of such instruments pursuant to the valuation hierarchy. Cash and Cash Equivalents The Company’s cash and cash equivalents are demand and money market accounts and other highly liquid investments with an original maturity of three months or less. Demand and money market accounts are at stated values. Fair values for other cash equivalents are classified as Level 1 and are based upon appropriate valuation methodology. Marketable Securities — Available-for-sale The Company classifies highly liquid money market funds, U.S. Treasury bonds and certificates of deposit within Level 1 of the fair value hierarchy because they are valued based on quoted market prices in active markets and upon models that take into consideration such market-based factors as recent sales, risk-free yield curves, and prices of similarly rated bonds. Commercial paper, corporate bonds, corporate debt securities, repurchase agreements, and asset backed securities are classified within Level 2 because they are valued using inputs other than quoted prices that are directly or indirectly observable in the market, including readily available pricing sources for the identical underlying security which may not be actively traded. The Company did not hold any securities classified within Level 3 as of March 31, 2022 (unaudited) and December 31, 2021. Public and Private Warrants At the Closing, Metromile Operating Company acquired the net liabilities from INSU, including warrants exercisable for common stock. The Company estimated the fair value of warrants exercisable for common stock measured at fair value on a recurring basis at the respective dates using the public trading price, for the Public warrants, and the Black-Scholes option valuation model, for the Private placement warrants (together with the public warrants, the “Warrants”), respectively. The Black-Scholes option valuation model inputs are based on the estimated fair value of the underlying common stock at the valuation measurement date, the remaining contractual term of the warrant, the risk-free interest rates, the expected dividends, and the expected volatility of the price of the Company’s underlying stock. These estimates, especially the expected volatility, are highly judgmental and could differ materially in the future. The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. The Company considers its Public warrants to be Level 1 liabilities as it uses publicly and readily available information to measure the fair value of the warrants. For the Company's Private placement warrants, while the Company believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date and as such are classified as Level 2 liabilities.

Overview and Basis of Presentation (Policies)

3 Months Ended

Mar. 31, 2022

The accompanying interim unaudited consolidated financial statements have been prepared in accordance GAAP and in accordance with the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). References to the Accounting Standard Codification (“ASC”) and Accounting Standard Updates (“ASU”) included hereinafter refer to the Accounting Standards Codification and Updates established by the Financial Accounting Standards Board (“FASB”) as the source of authoritative GAAP. The consolidated financial statements include the accounts of Metromile, Inc. and its subsidiaries, all of which are wholly owned. All intercompany accounts and transactions have been eliminated in consolidation.

These unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 ("the Company’s 2021 Annual Report").

Reclassifications

Reclassifications have been made to the prior year balances to conform to the current year presentation. In particular, accounts receivable, and digital assets, net have been combined with prepaid expenses and other assets into a single line on the consolidated balance sheets and consolidated statements of cash flows. The reclassifications had no effect on stockholders’ deficit or net loss after taxes as previously reported.

Use of Estimates

The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes. On an ongoing basis, the Company’s management evaluates estimates, including those related to contingent assets and liabilities as of the date of the financial statements as well as the reported amounts of revenue and expense during the reporting period. The Company’s principal estimates include: unpaid losses and LAE reserves; the fair value of investments; the fair value of stock-based awards; the fair value of the warrant liability; premium refunds to policyholders; reinsurance recoverable on unpaid loss; and the valuation allowance for income taxes. Because of uncertainties associated with estimating the amounts, timing and likelihood of possible outcomes, actual results could differ materially from these estimates.

Discontinued Operations and Held for Sale

A business is classified as held for sale when management having the authority to approve the action commits to a plan to sell the business, the sale is probable to occur during the next 12 months at a price that is reasonable in relation to its current fair value and certain other criteria are met. A business classified as held for sale is recorded at the lower of its carrying amount or estimated fair value less cost to sell. When the carrying amount of the business exceeds its estimated fair value less cost to sell, a loss is recognized and updated each reporting period as appropriate. The results of operations of business classified as held for sale are reported as discontinued operations if the disposal represents a strategic shift that will have a major effect on the entity’s operations and financial results.

Recently Issued Accounting Pronouncements

Reference Rate Reform

In March 2020, FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides optional expedients and exceptions to contract modifications and hedging relationships that reference LIBOR or another reference rate expected to be discontinued. The standard is effective upon issuance through December 31, 2022 and may be applied at the beginning of the interim period that includes March 12, 2020 or any date thereafter. The Company is currently evaluating this new standard and the impact it will have on its consolidated financial statements.

This standard may be elected and applied prospectively over time from March, 2020 through December 31, 2022 as reference rate reform activities occur. The Company is evaluating the method of adoption and impact of the standard on its consolidated financial statements and related disclosures.

Government Assistance

In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance. This update requires annual disclosures about transactions with a government that are accounted for by applying a grant or contribution accounting model by analogy. This standard is effective for annual periods beginning after December 15, 2021. Early adoption is permitted. The amendments should be applied either (1) prospectively to all transactions within the scope of the amendments that are reflected in financial statements at the date of initial application and new transactions that are entered into after the date of initial application or (2) retrospectively to those transactions. The Company is currently evaluating the impact of these amendments on its consolidated financial statements.

Fair Value Measurement

Topic 820, Fair Value Measurements, defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Topic 820 also establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value:

Level 1 — Quoted prices in active markets for identical assets or liabilities.

Level 2 — Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

An asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques used need to maximize the use of observable inputs and minimize the use of unobservable inputs.

The following is a description of the valuation methodologies used for instruments measured at fair value on a recurring basis and recognized in the accompanying Consolidated Balance Sheet, as well as the general classification of such instruments pursuant to the valuation hierarchy.

Cash and Cash Equivalents

The Company’s cash and cash equivalents are demand and money market accounts and other highly liquid investments with an original maturity of three months or less. Demand and money market accounts are at stated values. Fair values for other cash equivalents are classified as Level 1 and are based upon appropriate valuation methodology.

Marketable Securities — Available-for-sale

The Company classifies highly liquid money market funds, U.S. Treasury bonds and certificates of deposit within Level 1 of the fair value hierarchy because they are valued based on quoted market prices in active markets and upon models that take into consideration such market-based factors as recent sales, risk-free yield curves, and prices of similarly rated bonds. Commercial paper, corporate bonds, corporate debt securities, repurchase agreements, and asset backed securities are classified within Level 2 because they are valued using inputs other than quoted prices that are directly or indirectly observable in the market, including readily available pricing sources for the identical underlying security which may not be actively traded. The Company did not hold any securities classified within Level 3 as of March 31, 2022 (unaudited) and December 31, 2021.

Public and Private Warrants

At the Closing, Metromile Operating Company acquired the net liabilities from INSU, including warrants exercisable for common stock. The Company estimated the fair value of warrants exercisable for common stock measured at fair value on a recurring basis at the respective dates using the public trading price, for the Public warrants, and the Black-Scholes option valuation model, for the Private placement warrants (together with the public warrants, the “Warrants”), respectively. The Black-Scholes option valuation model inputs are based on the estimated fair value of the underlying common stock at the valuation measurement date, the remaining contractual term of the warrant, the risk-free interest rates, the expected dividends, and the expected volatility of the price of the Company’s underlying stock. These estimates, especially the expected volatility, are highly judgmental and could differ materially in the future.

The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. The Company considers its Public warrants to be Level 1 liabilities as it uses publicly and readily available information to measure the fair value of the warrants. For the Company's Private placement warrants, while the Company believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date and as such are classified as Level 2 liabilities.