Overview and Basis of Presentation (Policies)	9 Months Ended
Sep. 30, 2021
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.
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.
Digital Assets, Net	Digital Assets, Net During the nine months ended September 30, 2021, the Company purchased an aggregate of $1.0 million in digital assets, comprised solely of bitcoin. The Company currently accounts for these digital assets as indefinite-lived intangible assets in accordance with ASC 350, Intangibles—Goodwill and Other. The Company has ownership of and control over the purchased bitcoin asset and uses third-party custodial services to secure it. The digital assets are initially recorded at cost and are subsequently remeasured on the consolidated balance sheets at cost, net of any impairment losses incurred since acquisition. An impairment analysis is performed at each reporting period to identify whether events or changes in circumstances, in particular decreases in the quoted prices on active exchanges, indicate that it is more likely than not that digital assets held by the Company are impaired. The fair value of digital assets is determined on a nonrecurring basis in accordance with ASC 820, Fair Value Measurement, based on quoted prices on the active exchange(s) that the Company has determined is its principal market for bitcoin (Level 1 inputs). If the carrying value of the digital asset exceeds the fair value based on the lowest price quoted in the active exchanges during the period, an impairment loss has occurred with respect to those digital assets in the amount equal to the difference between their carrying values and the price determined. Impairment losses are recognized within Other expense in the consolidated statements of operations in the period in which the impairment is identified. The impaired digital assets are written down to their fair value at the time of impairment and this new cost basis will not be adjusted upward for any subsequent increase in fair value. Gains are not recorded until realized upon sale.
Recent Issued Accounting Pronouncements	Recent Issued Accounting Pronouncements As an emerging growth company (“EGC”), the Jumpstart Our Business Startups Act (the “JOBS Act”) allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are applicable to private companies. The Company has elected to use this extended transition period under the JOBS Act until such time as the Company is no longer considered to be an EGC. The adoption dates discussed below reflect this election. In February 2016, FASB issued ASU 2016-2, Leases (Topic 842). Lessees will need to recognize almost all leases on their balance sheet as a right-of-use asset and a lease liability. For income statement purposes, FASB retained a dual model, requiring leases to be classified as either operating or finance. Classification will be based on criteria that are largely similar to those applied in current lease accounting, but without explicit bright lines. Lessor accounting is similar to the current model but updated to align with certain changes to the lessee model and the new revenue recognition standard. The standard will be effective beginning after December 15, 2021. Early adoption is permitted. The Company is currently evaluating this new standard and the impact it will have on its consolidated financial statements. In June 2016, FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), intended to improve the timing, and enhance the accounting and disclosure, of credit losses on financial assets. This update modified the existing accounting guidance related to the impairment evaluation for available-for-sale debt securities, reinsurance recoverables, and premiums receivables and could result in the creation of an allowance for credit losses as a contra asset account. The ASU requires a cumulative-effect change to retained earnings in the period of adoption and prospective changes on previously recorded impairments, to the extent applicable. The amendments in ASU 2016-13 are effective for fiscal years beginning after December 15, 2022. The Company is currently evaluating this new standard and the impact it will have on its consolidated financial statements. In March 2020, FASB issued ASU 2020-4, 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.
Fair Value Measurement	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. 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)

9 Months Ended

Sep. 30, 2021

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.

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.

Digital Assets, Net

During the nine months ended September 30, 2021, the Company purchased an aggregate of $1.0 million in digital assets, comprised solely of bitcoin. The Company currently accounts for these digital assets as indefinite-lived intangible assets in accordance with ASC 350, Intangibles—Goodwill and Other. The Company has ownership of and control over the purchased bitcoin asset and uses third-party custodial services to secure it. The digital assets are initially recorded at cost and are subsequently remeasured on the consolidated balance sheets at cost, net of any impairment losses incurred since acquisition.

An impairment analysis is performed at each reporting period to identify whether events or changes in circumstances, in particular decreases in the quoted prices on active exchanges, indicate that it is more likely than not that digital assets held by the Company are impaired. The fair value of digital assets is determined on a nonrecurring basis in accordance with ASC 820, Fair Value Measurement, based on quoted prices on the active exchange(s) that the Company has determined is its principal market for bitcoin (Level 1 inputs). If the carrying value of the digital asset exceeds the fair value based on the lowest price quoted in the active exchanges during the period, an impairment loss has occurred with respect to those digital assets in the amount equal to the difference between their carrying values and the price determined.

Impairment losses are recognized within Other expense in the consolidated statements of operations in the period in which the impairment is identified. The impaired digital assets are written down to their fair value at the time of impairment and this new cost basis will not be adjusted upward for any subsequent increase in fair value. Gains are not recorded until realized upon sale.

Recent Issued Accounting Pronouncements

As an emerging growth company (“EGC”), the Jumpstart Our Business Startups Act (the “JOBS Act”) allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are applicable to private companies. The Company has elected to use this extended transition period under the JOBS Act until such time as the Company is no longer considered to be an EGC. The adoption dates discussed below reflect this election.

In February 2016, FASB issued ASU 2016-2, Leases (Topic 842). Lessees will need to recognize almost all leases on their balance sheet as a right-of-use asset and a lease liability. For income statement purposes, FASB retained a dual model, requiring leases to be classified as either operating or finance. Classification will be based on criteria that are largely similar to those applied in current lease accounting, but without explicit bright lines. Lessor accounting is similar to the current model but updated to align with certain changes to the lessee model and the new revenue recognition standard. The standard will be effective beginning after December 15, 2021. Early adoption is permitted. The Company is currently evaluating this new standard and the impact it will have on its consolidated financial statements.

In June 2016, FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), intended to improve the timing, and enhance the accounting and disclosure, of credit losses on financial assets. This update modified the existing accounting guidance related to the impairment evaluation for available-for-sale debt securities, reinsurance recoverables, and premiums receivables and could result in the creation of an allowance for credit losses as a contra asset account. The ASU requires a cumulative-effect change to retained earnings in the period of adoption and prospective changes on previously recorded impairments, to the extent applicable. The amendments in ASU 2016-13 are effective for fiscal years beginning after December 15, 2022. The Company is currently evaluating this new standard and the impact it will have on its consolidated financial statements.

In March 2020, FASB issued ASU 2020-4, 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.

Fair Value Measurement

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.

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.