| Summary of Significant Accounting Policies | Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements include Zillow Group, Inc. and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. These condensed consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these interim condensed consolidated financial statements should be read in conjunction with the audited financial statements and accompanying notes included in Zillow Group, Inc.’s Annual Report on Form 10-K for the year ended December 31, 2017 , which was filed with the SEC on February 15, 2018. The condensed consolidated balance sheet as of December 31, 2017 , included herein, was derived from the audited financial statements of Zillow Group, Inc. as of that date. The unaudited condensed consolidated interim financial statements, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary to present fairly our financial position as of March 31, 2018 , our results of operations, comprehensive loss and cash flows for the three month periods ended March 31, 2018 and 2017 . The results of the three month period ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any interim period or for any other future year. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make certain estimates, judgments and assumptions that affect the reported amounts of assets and liabilities and the related disclosures at the date of the financial statements, as well as the reported amounts of revenue and expenses during the periods presented. On an ongoing basis, we evaluate our estimates, including those related to the amortization period and recoverability of contract cost assets, website and software development costs, recoverability of long-lived assets and intangible assets with definite lives, share-based compensation, income taxes, business combinations, and the recoverability of goodwill and indefinite-lived intangible assets, among others. To the extent there are material differences between these estimates, judgments, or assumptions and actual results, our financial statements will be affected. Concentrations of Credit Risk Financial instruments, which potentially subject us to concentrations of credit risk, consist primarily of cash and cash equivalents, investments and accounts receivable. We place cash and cash equivalents and investments with major financial institutions, which management assesses to be of high credit quality, in order to limit exposure of our investments. Credit risk with respect to accounts receivable is dispersed due to the large number of customers. Further, our credit risk on accounts receivable is mitigated by the relatively short payment terms that we offer. Collateral is not required for accounts receivable. We maintain an allowance for doubtful accounts such that receivables are stated at net realizable value. Cash and Cash Equivalents Cash includes demand deposits with banks or financial institutions. Cash equivalents include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Our cash equivalents include only investments with original maturities of three months or less. We regularly maintain cash in excess of federally insured limits at financial institutions. Short-term Investments Our investments consist of fixed income securities, which include U.S. and foreign government agency securities, corporate notes and bonds, commercial paper, municipal securities and certificates of deposit, and are classified as available-for-sale securities. As the investments are available to support current operations, our available-for-sale securities are classified as short-term investments. Available-for-sale securities are carried at fair value with unrealized gains and losses reported as a component of accumulated other comprehensive loss in shareholders’ equity, while realized gains and losses and other-than-temporary impairments are reported as a component of net loss based on specific identification. An impairment charge is recorded in the consolidated statements of operations for declines in fair value below the cost of an individual investment that are deemed to be other than temporary. We assess whether a decline in value is temporary based on the length of time that the fair market value has been below cost, the severity of the decline and the intent and ability to hold or sell the investment. We did not identify any investments as other-than-temporarily impaired as of March 31, 2018 or December 31, 2017 . Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable represent our unconditional right to consideration. Accounts receivable are generally due within 30 days and are recorded net of the allowance for doubtful accounts. We consider accounts outstanding longer than the contractual terms past due. We review accounts receivable on a regular basis and estimate an amount of losses for uncollectible accounts based on our historical collections experience, age of the receivable, knowledge of the customer and the condition of the general economy and industry as a whole. We record changes in our estimate to the allowance for doubtful accounts through bad debt expense and relieve the allowance when accounts are ultimately determined to be uncollectible. Bad debt expense is included in general and administrative expenses. Contract Cost Assets We capitalize certain incremental costs of obtaining contracts with customers which we expect to recover. These costs relate to commissions paid to sales personnel, primarily for our Premier Agent and Premier Broker programs. As a practical expedient, we recognize the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that we otherwise would have recognized is one year or less. Capitalized commission costs are recorded as contract cost assets in our condensed consolidated balance sheets. Contract cost assets are amortized to expense on a straight-line basis over a period that is consistent with the transfer to the customer of the products or services to which the asset relates, generally the estimated life of the customer relationship. Amortization expense related to contract cost assets is included in sales and marketing expenses in our condensed consolidated statements of operations. In determining the estimated life of our customer relationships, we consider quantitative and qualitative data, including, but not limited to, historical customer data, recent changes or expected changes in product or service offerings, and changes in how we monetize our products and services. The amortization period for capitalized contract costs related to our Premier Agent and Premier Broker programs ranges from two to three years. Property and Equipment Property and equipment is recorded at cost and depreciated using the straight-line method over the estimated useful lives of the related assets. The useful lives are as follows: Computer equipment 2 to 3 years Office equipment, furniture and fixtures 5 to 7 years Leasehold improvements Shorter of expected useful life or lease term Maintenance and repair costs are charged to expense as incurred. Major improvements, which extend the useful life of the related asset, are capitalized. Upon disposal of a fixed asset, we record a gain or loss based on the difference between the proceeds received and the net book value of the disposed asset. Website and Software Development Costs The costs incurred in the preliminary stages of development are expensed as incurred. Once an application has reached the development stage, internal and external costs, if direct and incremental and deemed by management to be significant, are capitalized in property and equipment and amortized on a straight-line basis over their estimated useful lives. Maintenance and enhancement costs, including those costs in the post-implementation stages, are typically expensed as incurred, unless such costs relate to substantial upgrades and enhancements to the website or software that result in added functionality, in which case the costs are capitalized and amortized on a straight-line basis over the estimated useful lives. Amortization expense related to capitalized website and software development costs is included in technology and development expense. Capitalized development activities placed in service are amortized over the expected useful lives of those releases, currently estimated at one to three years. The estimated useful lives of website and software development activities are reviewed frequently and adjusted as appropriate to reflect upcoming development activities that may include significant upgrades and/or enhancements to the existing functionality. Construction-in-progress primarily consists of website development costs that are capitalizable, but for which the associated applications had not been placed in service. Recoverability of Goodwill and Indefinite-Lived Intangible Assets Goodwill represents the excess of the cost of an acquired business over the fair value of the assets acquired at the date of acquisition, and is not amortized. We assess the impairment of goodwill on an annual basis, in our fourth quarter, or whenever events or changes in circumstances indicate that goodwill may be impaired. Typically, we choose to forgo the initial qualitative assessment and perform a quantitative analysis to assist in our annual evaluation. If impairment exists, the carrying value of the goodwill is reduced to fair value through an impairment charge recorded in our statements of operations. Our indefinite-lived intangible asset is not amortized, and we assess the asset for impairment on an annual basis, in our fourth quarter, or whenever events or changes in circumstances indicate that the asset may be impaired. On an interim basis, we consider if there are any events and circumstances that could affect the significant inputs used to determine the fair value of the indefinite-lived intangible asset, including, but not limited to, costs that could have a negative effect on future expected earnings and cash flows, changes in certain key performance metrics, and changes in management, key personnel, strategy or customers. In our evaluation of our trade names and trademarks indefinite-lived intangible asset, we typically first perform a qualitative assessment to determine whether the fair value of the indefinite-lived intangible asset is more likely than not impaired. If so, we perform a quantitative assessment and an impairment charge is recorded in our statements of operations for the excess of the carrying value of the indefinite-lived intangible asset over its fair value. Intangible Assets We purchase and license data content from multiple data providers. This data content consists of U.S. county data about home details (e.g., the number of bedrooms, bathrooms, square footage) and other information relating to the purchase price of homes, both current and historical, as well as imagery, mapping and parcel data that is displayed on our mobile applications and websites. Our home details data not only provides information about a home and its related transactions which is displayed on our mobile applications and websites, but is also used in our proprietary valuation algorithms to produce Zestimates, Rent Zestimates and Zillow Home Value Indexes. License agreement terms vary by vendor. In some instances, we retain perpetual rights to this information after the contract ends; in other instances, the information and data are licensed only during the fixed term of the agreement. Additionally, certain data license agreements provide for uneven payment amounts throughout the contract term. We capitalize payments made to third parties for data licenses that we expect to provide future economic benefit through the recovery of the costs of these arrangements via the generation of our revenue and margins. For data license contracts that include uneven payment amounts, we capitalize the payments as they are made as an intangible asset and the total contract value is typically amortized on a straight-line basis over the term of the contract, which is equivalent to the estimated useful life of the asset. We evaluate data content contracts for potential capitalization at the inception of the arrangement as well as each time periodic payments to third parties are made. The amortization period for the capitalized purchased content is based on our best estimate of the useful life of the asset, which is approximately five years. The determination of the useful life includes consideration of a variety of factors including, but not limited to, our assessment of the expected use of the asset and contractual provisions that may limit the useful life, as well as an assessment of when the data is expected to become obsolete based on our estimates of the diminishing value of the data over time. We evaluate the useful life of the capitalized purchased data content each reporting period to determine whether events and circumstances warrant a revision to the remaining useful life. If we determine the estimate of the asset’s useful life requires modification, the carrying amount of the asset is amortized prospectively over the revised useful life. The capitalized purchased data content is amortized on a straight-line basis as the pattern of delivery of the economic benefits of the data cannot reliably be determined because we do not have the ability to reliably predict future traffic to our mobile applications and websites. Under certain other data agreements, the underlying data is obtained on a subscription basis with consistent monthly or quarterly recurring payment terms over the contractual period. Upon the expiration of such arrangements, we no longer have the right to access the related data, and therefore, the costs incurred under such contracts are not capitalized and are expensed as payments are made. We would immediately lose rights to data under these arrangements if we were to cancel the subscription and/or cease making payments under the subscription arrangements. We also capitalize costs related to the license of certain internal-use software from third parties, including certain licenses of software in cloud computing arrangements. Additionally, we capitalize costs incurred during the application development stage related to the development of internal-use software and enterprise cloud computing services. We expense costs as incurred related to the planning and post-implementation phases of development. Capitalized internal-use software costs are amortized over the estimated useful life of the asset, which is currently one to three years, on a straight-line basis. Intangibles-in-progress consist of purchased content and software that are capitalizable but have not been placed in service. We also have intangible assets for developed technology, customer relationships, trade names and trademarks and advertising relationships which we recorded in connection with acquisitions. Purchased intangible assets with a determinable economic life are carried at cost, less accumulated amortization. These intangible assets are amortized over the estimated useful life of the asset on a straight-line basis. Recoverability of Intangible Assets with Definite Lives and Other Long-Lived Assets We evaluate intangible assets and other long-lived assets for impairment whenever events or circumstances indicate that they may not be recoverable. Recoverability is measured by comparing the carrying amount of an asset group to future undiscounted net cash flows expected to be generated. We group assets for purposes of such review at the lowest level for which identifiable cash flows of the asset group are largely independent of the cash flows of the other groups of assets and liabilities. If this comparison indicates impairment, the amount of impairment to be recognized is calculated as the difference between the carrying value and the fair value of the asset group. Deferred Revenue Deferred revenue consists of prepaid advertising fees received or billed in advance of satisfying our performance obligations and prepaid but unrecognized subscription revenue. Deferred revenue is recognized when or as we satisfy our obligations under contracts with customers. Deferred Rent For our operating leases, we recognize rent expense on a straight-line basis over the terms of the leases and, accordingly, we record the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. For office space under an operating lease that is subleased to a third party for which we intend to reoccupy the space at a future date, rent expense is recognized net of sublease income. Landlord-funded leasehold improvements are also recorded as deferred rent liabilities and are amortized as a reduction of rent expense over the non-cancelable term of the related operating lease. Business Combinations We recognize identifiable assets acquired and liabilities assumed at their acquisition date fair values. Goodwill as of the acquisition date is measured as the excess of consideration transferred over the net of the acquisition date fair values of the assets acquired and the liabilities assumed. While we use our best estimates and assumptions for the purchase price allocation process to value assets acquired and liabilities assumed at the acquisition date, our estimates are inherently uncertain and subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, we record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill to the extent that we identify adjustments to the preliminary purchase price allocation. Upon the conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to our condensed consolidated statements of operations. We recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. Revenue Recognition We recognize revenue when (or as) we satisfy our performance obligations by transferring control of the promised products or services to our customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those products or services. We generate revenue from the sale of advertising services and our suite of marketing software and technology solutions to businesses and professionals primarily associated with the residential real estate, rental and mortgage industries. These professionals include real estate, rental and mortgage professionals and brand advertisers. Our four primary revenue categories are Premier Agent, Rentals, Mortgages and Other. As a practical expedient, we do not adjust the promised amount of consideration for the effects of a significant financing component as the period between our transfer of a promised product or service to a customer and when the customer pays for that product or service is one year or less. We do not disclose the transaction price related to remaining performance obligations for (i) contracts with an original expected duration of one year or less and (ii) contracts for which we recognize revenue at the amount to which we have the right to invoice for performance completed to date. The remaining duration of our performance obligations is generally less than one year. Premier Agent Revenue. Premier Agent revenue is derived from our Premier Agent and Premier Broker programs. Our Premier Agent and Premier Broker programs offer a suite of marketing and business technology products and services to help real estate agents and brokers achieve their advertising goals, while growing and managing their businesses and brands. All Premier Agents and Premier Brokers receive access to a dashboard portal on our mobile application or website that provides individualized program performance analytics, our customer relationship management, or CRM, tool that captures detailed information about each contact made with a Premier Agent or Premier Broker through our mobile and web platforms and our account management tools. We have concluded that the marketing and business technology products and services promised to Premier Agents and Premier Brokers represent distinct performance obligations. We offer our Premier Agent and Premier Broker advertising products on a cost per impression basis. Payment is received prior to the delivery of impressions. Impressions are delivered when a sold advertisement appears on pages viewed by users of our mobile applications and websites. We determine the cost per impression delivered in each zip code using an auction-based pricing method in consideration of the total amount spent by Premier Agents and Premier Brokers to purchase impressions in the zip code during the month. A Premier Agent’s or Premier Broker’s share of voice in a zip code is determined by their proportional monthly budgeted spend in that zip code as a percentage of the total monthly budgeted spend of all Premier Agents and Premier Brokers in that zip code. The cost per impression that we charge is dynamic - as demand for impressions in a zip code increases or decreases, the cost per impression in that zip code may be increased or decreased accordingly. The price paid for each impression is representative of the price at which we would sell an impression separately to a customer, or the stand-alone selling price. We have not allocated the transaction price to each performance obligation as the amounts recognized would be the same irrespective of any allocation. As such, we recognize revenue related to the Premier Agent and Premier Broker products and services based on the contractual spend recognized on a straight-line basis during the contractual period over which the products and services are provided. This methodology best depicts how we satisfy our performance obligations to customers, as we continuously transfer control of the performance obligations to the customer throughout the contractual period. Rentals Revenue. Rentals revenue includes our rentals marketplace and suite of tools for rental professionals. Rentals revenue primarily includes revenue generated by advertising sold to property managers and other rental professionals on a cost per lead, cost per click or cost per lease generated basis. We recognize revenue as leads or clicks are provided to rental professionals, which is the amount for which we have the right to invoice. The number of leases generated through our rentals marketplace during the period is accounted for as variable consideration, and we estimate these amounts based on the expected number of qualified leases secured during the period. We do not believe that a significant reversal in the amount of cumulative revenue recognized will occur once the uncertainty related to the number of leases secured is subsequently resolved. Mortgages Revenue. Mortgages revenue primarily includes marketing products sold to mortgage professionals on a cost per lead basis, including our Long Form and Custom Quote services. For our Long Form and Custom Quote cost per lead mortgage marketing products, participating qualified mortgage professionals typically make a prepayment to gain access to consumers interested in connecting with mortgage professionals. Mortgage professionals who exhaust their initial prepayment prepay additional funds to continue to participate in the marketplace. In Zillow Group’s Long Form platform, consumers answer a series of questions to find a local lender, and mortgage professionals receive consumer contact information, or leads, when the consumer chooses to share their information with a lender. Consumers who request rates for mortgage loans in Custom Quotes are presented with customized quotes from participating mortgage professionals. We recognize revenue when a user contacts a mortgage professional through Zillow Group’s mortgages platform, which is the amount for which we have the right to invoice. Mortgages revenue also includes revenue generated by Mortech, which provides subscription-based mortgage software solutions, including a product and pricing engine and lead management platform, for which we recognize revenue on a straight-line basis during the contractual period over which the services are provided. Other Revenue. Other revenue primarily includes revenue generated by new construction and display, as well as revenue from the sale of various other marketing and business products and services to real estate professionals. Our new construction marketing solutions allow home builders to showcase their available inventory to home shoppers. New construction revenue primarily includes revenue generated by advertising sold to builders on a cost per residential community basis, and revenue is recognized on a straight-line basis during the contractual period over which the communities are advertised on our mobile applications and websites. Consideration is billed in arrears. Display revenue primarily consists of graphical mobile and web advertising sold on a cost per thousand impressions or cost per click basis to advertisers promoting their brands on our mobile applications and websites. We recognize display revenue as clicks occur or as impressions are delivered to users interacting with our mobile applications or websites, which is the amount for which we have the right to invoice. Cost of Revenue Our cost of revenue consists of expenses related to operating our mobile applications and websites, including associated headcount expenses, such as salaries and benefits and share-based compensation expense and bonuses, as well as credit card fees, ad serving costs paid to third parties, revenue-sharing costs related to our commercial business relationships, depreciation expense and costs associated with the operation of our data center and mobile applications and websites. Technology and Development Technology and development expenses consist of headcount expenses, including salaries, benefits, share-based compensation expense and bonuses for salaried employees and contractors engaged in the design, development and testing of our mobile applications and websites, and equipment and maintenance costs. Technology and development expenses also include amortization costs related to capitalized website and development activities, amortization of software, amortization of certain intangibles and other data agreement costs related to the purchase of data used to populate our mobile applications and websites, amortization of intangible assets recorded in connection with acquisitions, including developed technology and customer relationships, amongst others, and depreciation expense. Share-Based Compensation We measure compensation expense for all share-based awards at fair value on the date of grant and recognize compensation expense over the service period on a straight-line basis for awards expected to vest. We use the Black-Scholes-Merton option-pricing model to determine the fair value for option awards. In valuing our option awards, we make assumptions about risk-free interest rates, dividend yields, volatility, and weighted-average expected lives. We account for forfeitures as they occur. Risk-free interest rates are derived from U.S. Treasury securities as of the option award grant date. Expected dividend yield is based on our historical cash dividend payments, which have been zero to date. The expected volatility for our Class A common stock and Class C capital stock is estimated using our historical volatility. The weighted-average expected life of the option awards is estimated based on our historical exercise data. For issuances of restricted stock units and restricted units, we determine the fair value of the award based on the market value of our Class A common stock or Class C capital stock, as applicable, at the date of grant. Advertising Costs Advertising costs are expensed as incurred. Advertising costs are recorded in sales and marketing expenses. Income Taxes We use the asset and liability approach for accounting and reporting income taxes, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement and tax bases of assets and liabilities at the applicable enacted tax rates. A valuation allowance against deferred tax assets would be established if, based on the weight of available evidence, it is more likely than not (a likelihood of more than 50%) that some or all of the deferred tax assets are not expected to be realized. We establish reserves for tax-related uncertainties based on estimates of whether, and the extent to which, additional taxes will be due. We adjust these reserves in light of changing facts and circumstances, such as the closing of a tax audit, new tax legislation or the change of an estimate. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made. Interest and penalties related to unrecognized tax benefits are recorded as income tax expense. On December 22, 2017, the U.S. government enacted comprehensive tax legislation under the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code, including but not limited to: (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) eliminating the corporate alternative minimum tax (“AMT”) and how AMT credits are utilized; (5) the additional limitations on deducting executive compensation under IRC Section 162(m); and (6) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017 . Shortly after enactment, implementation guidance was released by the Securities and Exchange Commission that requires a company to reflect the income tax effects of those aspects of the Tax Act for which the accounting under the accounting rules is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but the company is able to determine a reasonable estimate, it should record a provisional estimate in the financial statements. Further, the implementation guidance also provides for a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete their accounting pursuant to the accounting rules. Recently Adopted Accounting Standards In December 2016, the Financial Accounting Standards Board (“FASB”) issued guidance to narrow the definition of a business. This guidance assists entities with evaluating when a set of transferred assets and activities is a business. This guidance is effective for interim and annual reporting periods beginning after December 15, 2017, and early adoption is permitted. This guidance must be applied prospectively to transactions occurring within the period of adoption. We adopted this guidance on January 1, 2018. The adoption of this guidance did not have an impact on our financial position, results of operations or cash flows. In January 2016, the FASB issued guidance on the recognition and measurement of financial instruments. This guidance generally requires equity investments, except those accounted for under the equity method of accounting or those that |
