Basis of Presentation, Summary of Significant Accounting Policies and Change in Accounting Principle (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation In our opinion, the accompanying unaudited interim consolidated financial statements include all adjustments, consisting of normal recurring adjustments, which are necessary to fairly state our financial position, results of operations, and cash flows. The Consolidated Balance Sheet at December 31, 2016, has been derived from audited financial statements as of that date. The interim consolidated results of operations are not necessarily indicative of the results that may occur for the full fiscal year. Certain footnote disclosure normally included in financial statements prepared in accordance with United States of America generally accepted accounting principles (“GAAP”) has been omitted pursuant to instructions, rules, and regulations prescribed by the United States Securities and Exchange Commission (“SEC”). The disclosures provided herein should be read in conjunction with the audited financial statements and notes thereto included in our 2016 Form 10-K.
Accounting Estimates and Assumptions	Accounting Estimates and Assumptions The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions affecting the reported amounts of assets and liabilities and the disclosures of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses for the reporting period. Those estimates are inherently subject to change and actual results could differ from those estimates. In the accompanying consolidated financial statements, estimates are used for, but not limited to, the valuation of assets, liabilities, consideration related to business combinations and step acquisitions, revenue recognition including discounts and credits, estimated selling prices for deliverables in multiple element arrangements, contingent payments, allowance for doubtful accounts, depreciable lives of assets, impairment of long lived assets (including equity method investments), stock-based compensation, deferred income taxes and valuation allowance, contingent liabilities, valuation of intangible assets (including goodwill) and the useful lives of intangible assets.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Evolent Health, Inc. and its subsidiaries. All inter-company accounts and transactions are eliminated in consolidation.
Operating Segments	Operating Segments Operating segments are defined as components of a business that earn revenue and incur expenses for which discrete financial information is available that is evaluated, on a regular basis, by the chief operating decision maker (“CODM”) to decide how to allocate resources and assess performance. The Company’s CODM, the Chief Executive Officer, allocates resources at a consolidated level and therefore the Company views its operations and manages its business as one operating segment. All of the Company’s revenue is generated in the United States and all assets are located in the United States.
Restricted Cash and Restricted Investments	Restricted Cash and Restricted Investments Restricted cash and restricted investments are carried at cost and include cash and investments used to collateralize various contractual obligations
Goodwill	Goodwill We recognize the excess of the purchase price, plus the fair value of any non-controlling interests in the acquiree, over the fair value of identifiable net assets acquired as goodwill. Goodwill is not amortized, but is reviewed at least annually for indications of impairment, with consideration given to financial performance and other relevant factors. We perform impairment tests of goodwill at our single reporting unit level, which is consistent with the way management evaluates our business. Acquisitions to date have been complementary to the Company’s core business, and therefore goodwill is assigned to our single reporting unit to reflect the synergies arising from each business combination. As discussed in Note 3, we adopted Accounting Standards Update (“ASU”) 2017-04, Intangibles-Goodwill and Other - Simplifying the Test for Goodwill Impairment, effective January 1, 2017. The adoption resulted in an update to our accounting policy for goodwill impairment. Under the updated policy, we perform a one-step test in our evaluation of the carrying value of goodwill, if qualitative factors determine it is necessary to complete a goodwill impairment test. In the evaluation, the fair value of the relevant reporting unit is determined and compared to the carrying value. If the fair value is greater than the carrying value, then the carrying value is deemed to be recoverable, and no further action is required. If the fair value estimate is less than the carrying value, goodwill is considered impaired for the amount by which the carrying amount exceeds the reporting unit’s fair value and a charge is reported in impairment of goodwill on our Consolidated Statements of Operations. See Note 7 for additional discussion regarding goodwill impairment tests.
Adoption of New Accounting Standards and Adoption of New Accounting Standards	Adoption of New Accounting Standards In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other - Simplifying the Test for Goodwill Impairment. The purpose of the ASU is to simplify the subsequent measurement of goodwill. The ASU eliminates Step 2 from the goodwill impairment test. An entity no longer will determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. This update is effective for annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We believe this newly adopted principle is preferable as it reduces the complexity of performing a goodwill impairment test. As a result, we adopted this standard effective January 1, 2017. Our updated accounting policy for goodwill impairment is described in Note 2. While the adoption of this ASU may have a material impact in determining the results of future goodwill impairment tests and thus impact our consolidated financial statements in the future, there was no impact of the adoption during the three months ended March 31, 2017. In March 2016, the FASB issued ASU 2016-07, Investments-Equity Method and Joint Ventures - Simplifying the Transition to the Equity Method of Accounting. The purpose of this ASU is to eliminate the requirement to retroactively adopt the equity method of accounting when an investment qualifies for the equity method as a result of an increase in the level of ownership interest or degree of influence. The amendments require that the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor’s previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. Therefore, upon qualifying for the equity method of accounting, no retroactive adjustment of the investment is required. The amendments in this ASU are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. We adopted this standard effective January 1, 2017. The adoption did not have a material impact on our financial statements for the three months ended March 31, 2017. In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging - Contingent Put and Call Options in Debt Instruments. The purpose of this ASU is to clarify the requirements for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely rated to their debt hosts. An entity performing the assessment under the amendments in the ASU is required to assess the embedded call (put) options solely in accordance with the four-step decision sequence. For public business entities, the amendments in this ASU are effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. We adopted this standard effective January 1, 2017. The adoption did not have a material impact on our financial statements for the three months ended March 31, 2017. Future Adoption of New Accounting Standards In January 2017, the FASB issued ASU 2017-01, Business Combinations - Clarifying the Definition of a Business. The purpose of the ASU is to add guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The ASU provides a screen to determine when an integrated set of assets and activities is not a business. The ASU also provides a framework to assist entities in evaluating whether both an input and a substantive process are present. The amendments are effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The amendments should be applied prospectively on or after the effective date. We intend to adopt the requirements of this standard effective January 1, 2018, and are currently evaluating the impact on our consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows: Restricted Cash. The purpose of the ASU is to reduce diversity in practice regarding the classification and presentation of changes in restricted cash on the statement of cash flows. The amendments in the ASU require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The amendments are effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. The amendments in this ASU should be applied using a retrospective transition method to each period presented. We intend to adopt the requirements of this standard effective January 1, 2018, and are currently evaluating the impact of the adoption on our Consolidated Statements of Cash Flows. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments. This ASU provides updated guidance on eight specific cash flow issues to reduce diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The amendments are effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the amendments in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. We intend to adopt the requirements of this standard effective January 1, 2018, and are currently evaluating the impact of the adoption on our Consolidated Statements of Cash Flows. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments. With respect to assets measured at amortized cost, such as held-to-maturity assets, the update requires presentation of the amortized cost net of a credit loss allowance. The update eliminates the probable initial recognition threshold that was previously required prior to recognizing a credit loss on financial instruments. The credit loss estimate can now reflect an entity’s current estimate of all future expected credit losses as opposed to the previous standard, when an entity only considered past events and current conditions. With respect to available for sale debt securities, the update requires that credit losses be presented as an allowance rather than as a write-down. The update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted as of the fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. We intend to adopt the requirements of this standard effective January 1, 2020 and are currently evaluating the impact of the adoption on our financial condition and results of operations. In February 2016, the FASB issued ASU 2016-02, Leases, in order to establish the principles to report transparent and economically neutral information about the assets and liabilities that arise from leases. This update introduces a new standard on accounting for leases, including a lessee model that brings most leases on the balance sheet. The new standard also aligns many of the underlying principles of the new lessor model with those in ASC 606, the FASB’s new revenue recognition standard (e.g., those related to evaluating when profit can be recognized). The standard also requires lessors to increase the transparency of their exposure to changes in value of their residual assets and how they manage that exposure. The ASU is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted. We intend to adopt the requirements of this standard effective January 1, 2019, and are currently evaluating the impact of the adoption on our financial condition and results of operations. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, in order to clarify the principles of recognizing revenue. This standard establishes the core principle of recognizing revenue to depict the transfer of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The FASB defines a five-step process that systematically identifies the various components of the revenue recognition process, culminating with the recognition of revenue upon satisfaction of an entity’s performance obligation. By completing all five steps of the process, the core principles of revenue recognition will be achieved. In March 2016, the FASB issued an update to the new revenue standard (ASU 2014-09) in the form of ASU 2016-08, which amended the principal-versus-agent implementation guidance and illustrations in the new revenue guidance. The update clarifies that an entity should evaluate whether it is the principal or the agent for each specified good or service promised in a contract with a customer. In April 2016, the FASB issued another update to the new revenue standard in the form of ASU 2016-10, which amended the guidance on identifying performance obligations and the implementation guidance on licensing. These ASUs were followed by two further updates issued during May 2016: ASU 2016-11, which rescinds certain SEC guidance, such as the adoption of ASUs 2014-09 and 2014-16, including accounting for consideration given by a vendor to a customer, and ASU 2016-12, which is intended to clarify the objective of the collectability criterion while identifying the contract(s) with a customer. The new revenue standard (including updates) will be effective for annual and interim reporting periods beginning after December 15, 2017, with early adoption permitted only as of annual reporting periods beginning after December 15, 2016. We intend to adopt the requirements of this standard effective January 1, 2018, and while we are evaluating the impact to our financial condition and results of operations, we expect the adoption of this ASU to require the inclusion of additional disclosures surrounding the nature and timing of our revenue. In our efforts to adopt this ASU, we have formulated an implementation team that is currently engaged in the evaluation process. We have evaluated a number of our contracts and at this point there is no clear indication regarding overall impact to our consolidated financial statements. We intend to complete the process during 2017, and until we have a clear indication of the impact of the adoption of the new standard we will not finalize our implementation method. We have evaluated all other issued and unadopted ASUs and believe the adoption of these standards will not have a material impact on our results of operations, financial position, or cash flows.
Fair Value Measurement	Nonrecurring Fair Value Measurements In addition to the assets and liabilities that are recorded at fair value on a recurring basis, the Company records certain assets and liabilities at fair value on a nonrecurring basis as required by GAAP. Generally, assets are recorded at fair value on a nonrecurring basis as a result of impairment charges. This includes goodwill, intangible assets, property, plant and equipment, held-to-maturity investments and equity method investments. While not carried at fair value on a recurring basis, these items are continually monitored for indicators of impairment that would indicate current carrying value is greater than fair value. In those situations, the assets are considered impaired and written down to current fair value. Refer to Notes 4, 5, 6, 7 and 13 for further discussion of assets measured at fair value on a nonrecurring basis. Other Fair Value Disclosures The carrying amounts of cash and cash equivalents (those not held in a money market fund), restricted cash, receivables, prepaid expenses, accrued liabilities, accrued compensation and deferred rent approximate their fair values because of the relatively short-term maturities of these items and financial instruments.