Zillow (Z) 10-K 12 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 04, 2016	Jun. 30, 2015
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	ZG
Entity Registrant Name	Zillow Group, Inc.
Entity Central Index Key	1,617,640
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 4,380,916,635
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		53,320,939
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		6,217,447
Class C Capital Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		118,992,759

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 229,138	$ 125,765
Short-term investments	291,151	246,829
Accounts receivable, net of allowance for doubtful accounts of $3,378 and $2,811 at December 31, 2015 and 2014, respectively	29,789	18,684
Prepaid expenses and other current assets	24,016	10,059
Total current assets	574,094	401,337
Restricted cash	3,015
Long-term investments		83,326
Property and equipment, net	89,639	41,600
Goodwill	1,909,167	96,352
Intangible assets, net	554,765	26,757
Other assets	5,020	358
Total assets	3,135,700	649,730
Current liabilities:
Accounts payable	3,361	9,358
Accrued expenses and other current liabilities	43,047	16,883
Accrued compensation and benefits	11,392	6,735
Deferred revenue	21,450	15,356
Deferred rent, current portion	1,172	864
Total current liabilities	80,422	49,196
Deferred rent, net of current portion	13,743	11,755
Long-term debt	230,000
Deferred tax liabilities and other long-term liabilities	132,482
Total liabilities	$ 456,647	$ 60,951
Commitments and contingencies (Note 17)
Shareholders' equity:
Preferred stock, $0.0001 par value; 30,000,000 shares authorized as of December 31, 2015 and 2014; no shares issued and outstanding as of December 31, 2015 and 2014
Additional paid-in capital	$ 2,956,111	$ 716,498
Accumulated other comprehensive loss	(471)
Accumulated deficit	(276,605)	(127,731)
Total shareholders' equity	2,679,053	588,779
Total liabilities and shareholders' equity	3,135,700	649,730
Class A Common Stock
Shareholders' equity:
Common stock	5	3
Class B Common Stock
Shareholders' equity:
Common stock	1	1
Class C Capital Stock
Shareholders' equity:
Common stock	$ 12	$ 8

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts	$ 3,378	$ 2,811
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Class A Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	1,245,000,000	600,000,000
Common stock, shares issued	53,299,111	34,578,393
Common stock, shares outstanding	53,299,111	34,578,393
Class B Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	6,217,447	6,217,447
Common stock, shares outstanding	6,217,447	6,217,447
Class C Capital Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	600,000,000	0
Common stock, shares issued	118,958,359	81,591,680
Common stock, shares outstanding	118,958,359	81,591,680

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenue		$ 644,677	$ 325,893	$ 197,545
Costs and expenses:
Cost of revenue (exclusive of amortization)	[1]	61,614	29,461	18,810
Sales and marketing		307,089	169,462	108,891
Technology and development		198,565	84,669	48,498
General and administrative		170,445	65,503	37,919
Acquisition-related costs		16,576	21,493	376
Restructuring costs		35,551
Loss on divestiture of business		4,368
Total costs and expenses		794,208	370,588	214,494
Loss from operations		(149,531)	(44,695)	(16,949)
Other income		1,501	1,085	385
Interest expense		(5,489)
Loss before income taxes		(153,519)	(43,610)	(16,564)
Income tax benefit		4,645		4,111
Net loss		$ (148,874)	$ (43,610)	$ (12,453)
Net loss per share-basic and diluted		$ (0.88)	$ (0.36)	$ (0.12)
Weighted-average shares outstanding-basic and diluted		169,767	120,027	108,087
[1]	Amortization of website development costs and intangible assets included in technology and development $ 63,189 $ 29,487 $ 19,791

Consolidated Statements of Ope5

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Amortization of website development costs and intangible assets included in technology and development	$ 63,189	$ 29,487	$ 19,791

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (148,874)	$ (43,610)	$ (12,453)
Other comprehensive loss:
Unrealized losses on investments	(448)
Reclassification adjustment for net losses from investments included in net loss	(23)
Net unrealized losses on investments	(471)
Total other comprehensive loss	(471)
Comprehensive loss	$ (149,345)	$ (43,610)	$ (12,453)

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock: Class A Common Stock, Class B Common Stock and Class C Capital Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2012	$ 280,317	$ 10	$ 351,975	$ (71,668)
Beginning Balance (in shares) at Dec. 31, 2012		101,630,820
Issuance of common and capital stock upon exercise of stock options	18,350	$ 1	18,349
Issuance of common and capital stock upon exercise of stock options (in shares)		6,076,980
Issuance of restricted shares of common and capital stock	0	$ 0	0	0	$ 0
Issuance of restricted shares of common and capital stock (in shares)		756,342
Cancellation of restricted shares of common and capital stock	0	$ 0	0	0	0
Cancellation of restricted shares of common and capital stock (in shares)		(15,810)
Fair value of equity awards assumed in connection with an acquisition	430		430
Share-based compensation expense	27,253		27,253
Issuance of common and capital stock in connection with public offering, net of issuance costs of $12,900	253,899	$ 1	253,898
Issuance of common and capital stock in connection with public offering, net of issuance costs of $12,900 (in shares)		9,760,566
Net loss	(12,453)			(12,453)
Ending Balance at Dec. 31, 2013	567,796	$ 12	651,905	(84,121)
Ending Balance (in shares) at Dec. 31, 2013		118,208,898
Issuance of common and capital stock upon exercise of stock options	23,923		23,923
Issuance of common and capital stock upon exercise of stock options (in shares)		3,970,527
Issuance of common and capital stock related to vesting of restricted stock units	0	$ 0	0	0	0
Issuance of common and capital stock related to vesting of restricted stock units		208,095
Share-based compensation expense	40,670		40,670
Net loss	(43,610)			(43,610)
Ending Balance at Dec. 31, 2014	588,779	$ 12	716,498	(127,731)
Ending Balance (in shares) at Dec. 31, 2014		122,387,520
Issuance of common and capital stock in connection with an acquisition	1,883,728	$ 5	1,883,723
Issuance of common and capital stock in connection with an acquisition (in shares)		51,779,112
Issuance of common and capital stock upon exercise of stock options	24,423	$ 1	24,422
Equity award vesting acceleration in connection with restructuring	14,859		14,859
Issuance of common and capital stock upon exercise of stock options (in shares)		2,732,767
Fair value of equity awards assumed in connection with an acquisition	82,840		82,840
Debt premium recorded in additional paid-in capital in connection with an acquisition	126,386		126,386
Issuance of common and capital stock related to vesting of restricted stock units		1,899,531
Shares and value of restricted stock units withheld for tax liability	(8,150)		(8,150)
Shares and value of restricted stock units withheld for tax liability, share		(324,013)
Share-based compensation expense	115,533		115,533
Net loss	(148,874)			(148,874)
Other comprehensive loss	(471)				(471)
Ending Balance at Dec. 31, 2015	$ 2,679,053	$ 18	$ 2,956,111	$ (276,605)	$ (471)
Ending Balance (in shares) at Dec. 31, 2015		178,474,917

Consolidated Statements of Sha8

Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2013USD ($)
Statement of Stockholders' Equity [Abstract]
Stock issuance costs	$ 12,900

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (148,874)	$ (43,610)	$ (12,453)
Adjustments to reconcile net loss to net cash provided by operating activities, net of amounts assumed in connection with acquisitions:
Depreciation and amortization	75,386	35,624	23,254
Share-based compensation expense	105,214	34,085	23,436
Restructuring costs	19,001
Release of valuation allowance on certain deferred tax assets	(2,853)		(4,111)
Loss on disposal of property and equipment	1,384	505	910
Loss on divestiture of businesses, net	3,899
Bad debt expense	3,235	2,529	1,907
Deferred rent	2,553	4,415	400
Amortization of bond premium	2,487	3,506	624
Impairment of certain acquired intangible assets		3,259
Changes in operating assets and liabilities:
Accounts receivable	(1,051)	(5,979)	(7,571)
Prepaid expenses and other assets	(761)	(5,084)	(1,543)
Accounts payable	(11,158)	4,634	1,497
Accrued expenses and other current liabilities	(18,384)	6,282	(668)
Accrued compensation and benefits	(4,020)	2,295	1,706
Deferred revenue	(2,434)	3,058	3,910
Other long-term liabilities	(965)
Net cash provided by operating activities	22,659	45,519	31,298
Investing activities
Proceeds from maturities of investments	335,443	174,949	53,000
Purchases of investments	(307,658)	(272,644)	(236,147)
Proceeds from sales of investments	8,260
Decrease in restricted cash, net of amounts assumed in connection with an acquisition	3,931
Purchases of property and equipment	(54,981)	(32,595)	(22,047)
Purchases of intangible assets	(13,127)	(11,647)	(3,925)
Proceeds from divestiture of businesses	23,359
Cash acquired in acquisition, net	173,406
Cash paid for acquisitions, net	(104,192)	(3,500)	(42,708)
Net cash provided by (used in) investing activities	64,441	(145,437)	(251,827)
Financing activities
Proceeds from exercise of stock options	24,423	23,923	18,350
Value of equity awards withheld for tax liability	(8,150)
Proceeds from public offering, net of offering costs			253,899
Net cash provided by financing activities	16,273	23,923	272,249
Net increase (decrease) in cash and cash equivalents during period	103,373	(75,995)	51,720
Cash and cash equivalents at beginning of period	125,765	201,760	150,040
Cash and cash equivalents at end of period	229,138	125,765	201,760
Supplemental disclosures of cash flow information
Cash paid for interest	6,325
Noncash transactions:
Value of Class A common stock issued in connection with an acquisition	1,883,728
Capitalized share-based compensation	10,319	6,585	3,817
Write-off of fully depreciated property and equipment	$ 26,242	$ 4,749	$ 3,697

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Organization and Description of Business	Note 1. Organization and Description of Business Zillow Group, Inc. (the “Company,” “Zillow Group,” “we,” “us” and “our”) operates the leading real estate and home-related information marketplaces on mobile and the Web, with a complementary portfolio of brands and products to help people find vital information about homes and connect with local professionals. Zillow Group’s brands focus on all stages of the home lifecycle: renting, buying, selling, financing and home improvement. The Zillow Group portfolio of consumer brands includes real estate and rental marketplaces Zillow, Trulia, StreetEasy and HotPads. In addition, Zillow Group works with tens of thousands of real estate agents, mortgage and rental professionals, helping maximize business opportunities and connect to millions of consumers. We also own and operate a number of brands for real estate, rental and mortgage professionals, including DotLoop, Mortech, Diverse Solutions and Retsly. Acquisition of Trulia, Inc. Effective February 17, 2015, pursuant to the Agreement and Plan of Merger dated as of July 28, 2014 (the “Merger Agreement”) by and among Zillow, Inc. (“Zillow”), Zillow Group, and Trulia, Inc. (“Trulia”), each of Zillow and Trulia became wholly owned subsidiaries of Zillow Group. Upon completion of the acquisition, each outstanding share of Class A common stock of Zillow was converted into the right to receive one share of fully paid and nonassessable Class A common stock of Zillow Group, each outstanding share of Class B common stock of Zillow was converted into the right to receive one share of fully paid and nonassessable Class B common stock of Zillow Group, and each outstanding share of Trulia common stock was converted into the right to receive 0.444 of a share of fully paid and nonassessable Class A Common Stock of Zillow Group. In addition, subject to certain exceptions, each Trulia stock option, restricted stock unit and stock appreciation right outstanding upon the consummation of the acquisition, whether or not vested and exercisable, was assumed by Zillow Group and converted into a corresponding equity award to purchase, acquire shares of, or participate in the appreciation in price of Zillow Group Class A Common Stock. The terms of each such assumed equity award are the same except that the number of shares subject to each equity award and the per share exercise price, if any, were adjusted based on the exchange ratio of 0.444 per a formula set forth in the Merger Agreement. Generally, each Zillow stock option and restricted stock unit outstanding upon the consummation of the acquisition, whether or not vested or exercisable, was assumed by Zillow Group and converted into a corresponding equity award to purchase or acquire shares of Zillow Group Class A common stock. The terms of each such assumed equity award are the same. Any unvested shares of Zillow Class A common stock subject to a repurchase option, risk of forfeiture or other condition as of the consummation of the acquisition were exchanged for shares of Zillow Group Class A common stock that are also unvested and subject to the same repurchase option, risk of forfeiture or other condition. Each Zillow restricted unit outstanding as of the consummation of the acquisition was assumed by Zillow Group and converted into the right to receive Zillow Group Class A common stock, subject to the same terms as the original restricted unit. The total purchase price of Trulia was approximately $2.0 billion. We have included Trulia’s results of operations prospectively after February 17, 2015, the date of acquisition. Further details on the acquisition of Trulia are presented in Note 7 of these consolidated financial statements. On February 17, 2015, in connection with the acquisition, Zillow Group undertook a restructuring plan that resulted in a total workforce reduction of nearly 350 employees, primarily to eliminate overlapping positions in the sales and marketing functions related to Trulia’s workforce at its Bellevue, Denver, New York and San Francisco locations. The restructuring plan is a result of the integration of Trulia’s business and operations with and into Zillow Group’s business. Employees directly affected by the restructuring plan have been provided with severance payments, stock vesting acceleration and outplacement assistance. As of December 31, 2015, the restructuring plan is substantially complete. Further details on the restructuring plan are presented in Note 18 of these consolidated financial statements. Certain Significant Risks and Uncertainties We operate in a dynamic industry and, accordingly, can be affected by a variety of factors. For example, we believe that changes or developments in any of the following areas could have a significant effect on us in terms of our future financial position, results of operations or cash flows: rates of revenue growth; engagement and usage of our products; scaling and adaptation of existing technology and network infrastructure; competition in our market; our ability to successfully integrate and realize the benefits of our past or future strategic acquisitions or investments, including our February 2015 acquisition of Trulia; management of our growth; our ability to attract and retain qualified employees and key personnel; protection of our brand and intellectual property; changes in government regulation affecting our business; the outcome of claims asserted against us in litigation; intellectual property infringement and other claims; protection of customers’ information and privacy concerns; and security measures related to our mobile applications and websites, among other things.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements include Zillow Group, Inc. and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. These consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”). For financial reporting and accounting purposes, Zillow was the acquirer of Trulia. The results presented in the consolidated financial statements and the notes to consolidated financial statements reflect those of Zillow prior to the completion of the acquisition of Trulia on February 17, 2015, and Trulia’s results of operations have been included prospectively after February 17, 2015. On August 14, 2015, Zillow Group completed a stock dividend in the form of two shares of Class C capital stock for each share of Class A common stock and Class B common stock outstanding as of July 31, 2015. The stock dividend had the effect of a 3-for-1 stock split. All references made to share or per share amounts in the accompanying consolidated financial statements and applicable disclosures have been retroactively adjusted to reflect the stock split. See Note 12, Note 14 and Note 15 for additional information about the stock split effected in the form of a stock dividend. 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 revenue recognition, website development costs, recoverability of long-lived assets and intangible assets with definite lives, share-based compensation, income taxes, business combinations, goodwill, and restructuring, among others. To the extent there are material differences between these estimates, judgments, or assumptions and actual results, our financial statements will be affected. Reclassifications Certain immaterial reclassifications have been made in the consolidated statements of operations and statements of cash flows to conform data for prior periods to the current format. 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. Restricted Cash Restricted cash consists of certificates of deposit held as collateral in our name at a financial institution related to certain of our operating leases. Investments Our investments consist of fixed income securities, which include U.S. and foreign government agency securities, corporate notes and bonds, municipal securities, commercial paper and certificates of deposit, and are classified as available-for-sale securities beginning on January 1, 2015. 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 December 31, 2015 or December 31, 2014. Prior to January 1, 2015 our investments were classified as held-to-maturity and were recorded at amortized cost (see Note 4). Accounts Receivable and Allowance for Doubtful Accounts 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. 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 3 years Purchased software 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 differences 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 year. 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. Goodwill Goodwill represents the excess of the cost of an acquired business over the fair value of the assets acquired at the date of acquisition. 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. We assess goodwill for possible impairment by first performing a qualitative assessment to determine whether it is more likely than not that the fair value of our reporting unit is less than its carrying amount. If we determine that it is not more likely than not that the fair value of our reporting unit is less than its carrying amount, then the first and second steps of the goodwill impairment test are unnecessary. If we determine that it is more likely than not that the fair value of our reporting unit is less than its carrying amount, we perform the two-step goodwill impairment test. The first step of the goodwill impairment test identifies if there is potential goodwill impairment. If step one indicates that an impairment may exist, a second step is performed to measure the amount of the goodwill impairment, if any. Goodwill impairment exists when the estimated fair value of goodwill is less than its carrying value. If impairment exists, the carrying value of the goodwill is reduced to fair value through an impairment charge recorded in our statements of operations. 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 life of 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 amortize the total contract value over the estimated useful life. For contracts in which we have perpetual rights to the data, the total contract value is amortized on a straight-line basis over the life of the contract plus two years, which is equivalent to the estimated useful life of the asset. For contracts in which we do not have access to the data beyond the contractual term, the total contract value is amortized on a straight line basis over the term of the contract. 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 ranges from two to nine 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 websites and mobile applications. 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 have intangible assets for developed technology, customer relationships, trade names and trademarks, advertising relationships and MLS home data feeds 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 the delivery or completion of the services, prepaid but unrecognized subscription revenue, and for amounts received in instances when revenue recognition criteria have not been met. Deferred revenue is recognized when the services are provided and all revenue recognition criteria have been met. 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. Restructuring The main components of our restructuring plan related to the February 2015 acquisition of Trulia relate to workforce reduction and contract termination costs. Workforce reduction charges are accrued when it is probable that the employees are entitled to the severance payments and the amounts can be reasonably estimated. One-time involuntary termination benefits are accrued when the plan of termination has been communicated to the employees and certain other criteria are met. Share-based compensation expense related to acceleration of share-based awards assumed in connection with the acquisition of Trulia is recognized over the remaining requisite service period. Contract termination costs are recognized as a liability when a contract is terminated in accordance with its terms or at the cease-use date. The cumulative effect of a change resulting from a revision to either the timing or the amount of estimated cash flows is recognized as an adjustment to the liability in the period of the change. If the amounts and timing of cash flows from restructuring activities are significantly different from what we have estimated, the actual amount of restructuring and other related charges could be materially different than those we have recorded. Further details on the restructuring are presented in Note 18 of these consolidated financial statements. 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 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. Further details on the February 2015 acquisition of Trulia and the August 2015 acquisition of DotLoop, Inc. are presented in Note 7 of these consolidated financial statements. Revenue Recognition In general, we recognize revenue when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered to the customer, (iii) the fee is fixed or determinable, and (iv) collectability is reasonably assured. We consider a signed agreement, a binding insertion order or other similar documentation reflecting the terms and conditions under which products or services will be provided to be persuasive evidence of an arrangement. Collectability is assessed based on a number of factors, including payment history and the creditworthiness of a customer. If it is determined that collection is not reasonably assured, revenue is not recognized until collection becomes reasonably assured, which is generally upon receipt of cash. We generate revenue from the sale of advertising services and our suite of tools to businesses and professionals primarily associated with the real estate and mortgage industries. These professionals include local real estate professionals, mortgage professionals and brand advertisers. Our two revenue categories are marketplace revenue and display revenue. Incremental direct costs incurred related to the acquisition or origination of a customer contract in a transaction that results in the deferral of revenue are expensed as incurred. Marketplace Revenue. Real estate revenue primarily includes revenue from advertising and a suite of tools sold to real estate professionals, as well as revenue generated by Zillow Group Rentals, which includes our rentals marketplace and suite of tools for rental professionals. In August 2015, Zillow Group completed the integration of certain Zillow and Trulia agent advertising products, effectively eliminating the Trulia Local Ads and Trulia Mobile Ads products. As a result of the integration, Agent Advertisers can manage their advertising across both Zillow and Trulia mobile and Web through the combined Premier Agent platform. Our Zillow Premier Agent program, which is included in real estate revenue, offers a suite of marketing and business technology solutions to help real estate agents grow their businesses and personal brands. The Premier Agent program allows agents to select products and services that they can tailor to meet their business and advertising needs. The program has three tiers of participation including Premier Platinum, our flagship product, as well as Premier Gold and Premier Silver, to meet different marketing and business needs of a broad range of agents. All tiers of Premier Agents receive access to a dashboard portal on our website that provides individualized program performance analytics, as well as our personalized website service, and our free customer relationship management, or CRM, tool that captures detailed information about each contact made with a Premier Agent through our mobile and web platforms. Our Premier Gold product also includes featured listings whereby the agent’s listings will appear at the top of search results on our mobile and web platforms. Our Premier Platinum product includes the dashboard portal on our website, our personalized website service, our CRM tool, featured listings, and inclusion on our buyer’s agent list, whereby the agent appears as the agent to contact for listings in the purchased zip code. We charge for our Platinum Premier Agent product based on the number of impressions delivered on our buyer’s agent list in zip codes purchased and a contracted maximum cost per impression. Our Platinum Premier Agent product includes multiple deliverables which are accounted for as a single unit of accounting, as the delivery or performance of the undelivered elements is based on traffic to our mobile applications and websites. We recognize revenue related to our impression-based Platinum Premier Agent product based on the lesser of (i) the actual number of impressions delivered on our buyer’s agent list during the period multiplied by the contracted maximum cost per impression, or (ii) the contractual maximum spend on a straight-line basis during the contractual period over which the services are delivered, typically over a period of six months or twelve months and then month-to-month thereafter. We charge a fixed subscription fee for Zillow’s Premier Gold and Premier Silver subscription products. Subscription advertising revenue for our Premier Gold and Premier Silver subscription products is recognized on a straight-line basis during the contractual period over which the services are delivered, typically over a period of six months and then month-to-month thereafter. Our Trulia real estate products included in real estate revenue are primarily sold on a fixed fee subscription basis, and include Trulia Local Ads, Trulia Mobile Ads, Trulia Pro with featured listings and Trulia Seller Ads. Prior to the August 2015 integration of certain of Zillow’s and Trulia’s advertising products, Trulia Local Ads and Trulia Mobile Ads enabled real estate professionals to promote themselves on Trulia’s search results pages and property details pages for a local market area. Real estate professionals purchased subscriptions to these products based upon their specified market share for a city or zip code, at a fixed monthly price, for periods ranging from one month to one year, with pricing depending on demand, location, and the percentage of market share purchased. Following the August 2015 agent advertising product integration, Trulia Local Ads and Trulia Mobile Ads products are no longer sold by Zillow Group. Trulia’s featured listings product allows real estate professionals to receive prominent placement of their listings in Trulia’s search results. Real estate professionals sign up for new subscriptions to this product at a fixed monthly price for periods that generally range from six months to 12 months. Trulia Seller Ads enable real estate professionals to generate leads from consumers interested in selling their homes. Subscription advertising revenue for Trulia’s real estate products included in real estate revenue is recognized on a straight-line basis during the contractual period over which the services are delivered. Rentals revenue, which is included in real estate revenue, primarily includes advertising sold to property managers and other rental professionals on a cost per lead and cost per lease generated basis. We recognize revenue as leads are delivered to rental professionals or as qualified leases are confirmed. Mortgages revenue primarily includes advertising sold to mortgage lenders and other mortgage professionals on a cost per lead basis, as well as 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 delivered. For our cost per lead mortgage advertising products, participating qualified mortgage professionals make a prepayment to gain access to consumers interested in connecting with mortgage professionals. Consumers who request rates for mortgage loans are presented with personalized quotes from participating mortgage professionals. We only charge mortgage professionals a fee when users contact mortgage professionals for more information regarding a mortgage loan quote. Mortgage professionals who exhaust their initial prepayment can then prepay additional funds to continue to participate in the marketplace. We recognize revenue when a user contacts a mortgage professional through Zillow Group’s mortgages platform. Market Leader revenue primarily includes revenue from the sale of a comprehensive premium software-as-a-service based marketing product typically sold to real estate professionals as a bundle of products under a fixed fee subscription. Market Leader revenue is included in our results of operations from February 17, 2015 through the date of divestiture of September 30, 2015 (see Note 8). Display Revenue. There were no customers that generated 10% or more of our total revenue in the years ended December 31, 2015, 2014 or 2013. 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, costs to generate leads for customers, multiple listing services fees and costs associated with the operation of our data center and customer websites. Technology and Development Research and development costs are expensed as incurred and are recorded in technology and development expenses. These costs consist primarily of technology and development headcount related expenses including salaries, bonuses, benefits and share-based compensation expense primarily associated with developing new technologies. For the years ended December 31, 2015, 2014 and 2013, expenses attributable to research and development for our business totaled $163.8 million, $72.9 million and $41.7 million, respectively. Technology and development expenses also include amortization of intangible assets, including acquired intangible assets, purchased content and capitalized website development costs, and other data content 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, including estimated forfeiture rates. 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 a combination of our historical volatility and the published historical volatilities of industry peers in the online publishing market representing the verticals in which we operate. Through June 30, 2015, we estimated the weighted-average expected life of the option awards as the average of the option vesting schedule and the term of the award, since we did not have sufficient historical exercise data to provide a reasonable basis upon which to estimate expected term due to the limited period of time share-based awards had been exercisable. Beginning July 1, 2015, we estimate the weighted-average expected life of the option awards based on our historical exercise data. Forfeiture rates are estimated using historical actual forfeiture trends as well as our judgment of future forfeitures. These rates are evaluated at least quarterly and any change in compensation expense is recognized in the period of the change. The estimation of option awards that will ultimately vest requires judgment, and to the extent actual results or updated estimates differ from our current estimates, such amounts will be recorded as a cumulative adjustment in the period the estimates are revised. We consider many factors when estimating expected forfeitures, including employee class and historical experience. Actual results, and future changes in estimates, may differ substantially from management’s current estimates. For issuances of restricted stock awards, 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 at the date of grant. Advertising Costs Advertising costs are expensed as incurred. For the years ended December 31, 2015, 2014 and 2013, expenses attributable to advertising totaled $103.4 million, $73.1 million and $38.7 million, respectively. 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. Recently Issued Accounting Standards In November 2015, the Financial Accounting Standards Board (“FASB”) issued guidance on the balance sheet classification of deferred taxes. This standard requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. This guidance is effective for interim and annual reporting periods beginning after December 15, 2016, and early adoption is permitted. We adopted this guidance for the year ended December 31, 2015 on a retrospective basis. The adoption of this guidance has not had a material impact on our financial position, results of operations or cash flows, and did not have any effect on prior periods due to the full valuation allowance against our net deferred tax assets. In September 2015, the FASB issued guidance on simplifying the accounting for measurement-period adjustments in business combinations. This standard requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the repo

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 3. Fair Value Measurements Accounting standards define fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market in an orderly transaction between market participants on the measurement date. The standards also establish a fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. There are 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—Assets and liabilities valued based on observable market data for similar instruments, such as quoted prices for similar assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity; instruments valued based on the best available data, some of which is internally developed, and considers risk premiums that a market participant would require. We applied the following methods and assumptions in estimating our fair value measurements: Cash equivalents Investments Restricted cash The following table presents the balances of assets measured at fair value on a recurring basis, by level within the fair value hierarchy, as of December 31, 2015 (in thousands): December 31, 2015 Total Level 1 Level 2 Cash equivalents: Money market funds $ 195,870 $ 195,870 $ — Certificates of deposit 1,622 — 1,622 Short-term investments: U.S. government agency securities 194,636 194,636 — Corporate notes and bonds 41,314 — 41,314 Municipal securities 39,853 — 39,853 Certificates of deposit 11,837 — 11,837 Foreign government securities 3,511 — 3,511 Restricted cash 3,015 — 3,015 Total $ 491,658 $ 390,506 $ 101,152 The following table presents the fair value, by level within the fair value hierarchy, of our cash equivalents and investments as of December 31, 2014 (in thousands): December 31, 2014 Total Level 1 Level 2 Cash equivalents: Money market funds $ 98,645 $ 98,645 $ — Foreign government securities 9,035 — 9,035 Certificates of deposit 2,975 — 2,975 Short-term investments: U.S. government agency securities 118,342 118,342 — Corporate notes and bonds 78,746 — 78,746 Municipal securities 26,256 — 26,256 Foreign government securities 8,570 — 8,570 Commercial paper 7,987 — 7,987 Certificates of deposit 6,928 — 6,928 Long-term investments: U.S. government agency securities 63,515 63,515 — Municipal securities 12,917 — 12,917 Corporate notes and bonds 6,694 — 6,694 Certificates of deposit 200 — 200 Total $ 440,810 $ 280,502 $ 160,308 See Note 12 for the carrying amount and estimated fair value of the Company’s convertible senior notes. We did not have any Level 3 assets as of December 31, 2015 or 2014. There were no liabilities measured at fair value as of December 31, 2015 or 2014.

Cash, Cash Equivalents, Investm

Cash, Cash Equivalents, Investments and Restricted Cash	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Cash, Cash Equivalents, Investments and Restricted Cash	Note 4. Cash, Cash Equivalents, Investments and Restricted Cash On January 1, 2015 we transferred our cash equivalent and investment portfolio of approximately $440.8 million from held-to-maturity to available-for-sale, which resulted in the recognition of an insignificant loss of $0.1 million. The transfer of the investment portfolio to available-for-sale was made to provide increased flexibility in the use of our investments to support current operations. 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. The following table presents the amortized cost, gross unrealized gains and losses, and estimated fair market value of our cash and cash equivalents, available-for-sale investments and restricted cash as of December 31, 2015 (in thousands): December 31, 2015 Amortized Gross Gross Estimated Cash $ 31,646 $ — $ — $ 31,646 Cash equivalents: Money market funds 195,870 — — 195,870 Certificates of deposit 1,622 — — 1,622 Short-term investments: U.S government agency securities 195,092 1 (457 ) 194,636 Corporate notes and bonds 41,390 1 (77 ) 41,314 Municipal securities 39,878 11 (36 ) 39,853 Certificates of deposit 11,839 1 (3 ) 11,837 Foreign government securities 3,516 — (5 ) 3,511 Restricted cash 3,015 — — 3,015 Total $ 523,868 $ 14 $ (578 ) $ 523,304 As of December 31, 2014, the amortized cost of cash equivalents and held-to-maturity investments approximated their fair value. The following table presents available-for-sale investments by contractual maturity date as of December 31, 2015 (in thousands): Amortized Cost Estimated Fair Market Value Due in one year or less $ 140,656 $ 140,551 Due after one year through two years 151,059 150,600 Total $ 291,715 $ 291,151

Accounts Receivable, Net

Accounts Receivable, Net	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Accounts Receivable, Net	Note 5. Accounts Receivable, Net The following table presents the detail of accounts receivable as of the dates presented (in thousands): December 31, 2015 2014 Accounts receivable $ 30,740 $ 17,373 Unbilled accounts receivable 2,427 4,122 Less: allowance for doubtful accounts (3,378 ) (2,811 ) Accounts receivable, net $ 29,789 $ 18,684 The following table presents the changes in the allowance for doubtful accounts for the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Allowance for doubtful accounts: Balance, beginning of period $ 2,811 $ 1,850 $ 965 Additions charged to expense 3,235 2,529 1,907 Less: write-offs, net of recoveries and other adjustments (2,668 ) (1,568 ) (1,022 ) Balance, end of period $ 3,378 $ 2,811 $ 1,850

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Note 6. Property and Equipment, Net The following table presents the detail of property and equipment as of the dates presented (in thousands): December 31, 2015 2014 Website development costs $ 74,750 $ 65,224 Computer equipment 20,965 13,243 Leasehold improvements 32,918 10,617 Software 6,961 3,431 Construction-in-progress 15,630 9,307 Office equipment, furniture and fixtures 13,495 6,482 Property and equipment 164,719 108,304 Less: accumulated amortization and depreciation (75,080 ) (66,704 ) Property and equipment, net $ 89,639 $ 41,600 We recorded depreciation expense related to property and equipment (other than website development costs) of $12.2 million, $6.1 million and $3.5 million, respectively, during the years ended December 31, 2015, 2014 and 2013. We capitalized $46.1 million, $22.2 million and $17.3 million, respectively, in website and software development costs during the years ended December 31, 2015, 2014 and 2013. Amortization expense for website and software development costs included in technology and development expenses was $23.9 million, $18.3 million and $12.2 million, respectively, for the years ended December 31, 2015, 2014 and 2013. Construction-in-progress primarily consists of website development costs that are capitalizable, but for which the associated applications had not been placed in service.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions	Note 7. Acquisitions During the year ended December 31, 2015, we acquired Trulia, Inc. (“Trulia”) and DotLoop, Inc. (“DotLoop”). Acquisition-related costs incurred, which primarily included investment banker fees, legal, accounting, tax, regulatory filing and printing fees, were expensed as incurred. Total acquisition-related costs of $16.6 million for the year ended December 31, 2015 are included as a separate line item in our consolidated statement of operations, and primarily relate to the February 2015 acquisition of Trulia. Acquisition of Trulia Effective February 17, 2015, pursuant to the Merger Agreement dated as of July 28, 2014 by and among Zillow, Zillow Group and Trulia, following the consummation of the transactions contemplated by the Merger Agreement, each of Zillow and Trulia became wholly owned subsidiaries of Zillow Group. Prior to the closing, Zillow Group formed two wholly owned subsidiaries, Zebra Merger Sub, Inc. and Tiger 1 Merger Sub, Inc. Pursuant to the Merger Agreement, Zebra Merger Sub, Inc. merged with and into Zillow (the “Zillow Merger”), Zebra Merger Sub, Inc. ceased to exist, and Zillow is the surviving corporation, and Tiger 1 Merger Sub, Inc. merged with and into Trulia (the “Trulia Merger”), Tiger 1 Merger Sub, Inc. ceased to exist, and Trulia is the surviving corporation. The acquisition of Trulia aligns with our growth strategies, including focusing on consumers and deepening, strengthening, and expanding our marketplaces. With the addition of Trulia, we expanded our audience and added another consumer brand that offers buyers, sellers, homeowners and renters access to information about homes and real estate for free, and provides advertising and software solutions that help real estate professionals grow their business. At the effective time of the Zillow Merger, each share of Zillow Class A common stock, other than Zillow excluded shares (as defined below), was converted into the right to receive one share of fully paid and nonassessable Zillow Group Class A common stock, and each share of Zillow Class B common stock, other than Zillow excluded shares, was converted into the right to receive one share of fully paid and nonassessable Zillow Group Class B common stock. Shares of Zillow common stock held by Zillow as treasury stock or by Zillow Group, Trulia, or any direct or indirect wholly owned subsidiary of Zillow or Trulia (“Zillow excluded shares”) were canceled and did not receive the Zillow merger consideration. Generally, each Zillow stock option and restricted stock unit outstanding (whether or not vested or exercisable) as of the effective time of the Zillow Merger was assumed by Zillow Group and converted into a corresponding equity award to purchase or acquire shares of Zillow Group Class A common stock, subject to the same terms, conditions and restrictions as the original option or award. Any unvested shares of Zillow Class A common stock subject to a repurchase option, risk of forfeiture or other condition as of the effective time of the Zillow Merger were exchanged for shares of Zillow Group Class A common stock that are also unvested and subject to the same repurchase option, risk of forfeiture or other condition. Each Zillow restricted unit outstanding as of the effective time of the Zillow Merger was assumed by Zillow Group and converted into the right to receive Zillow Group Class A common stock, subject to the same terms, conditions and restrictions as the original restricted unit. At the effective time of the Trulia Merger, each share of Trulia common stock, other than Trulia excluded shares (as defined below), was converted into the right to receive 0.444 of a share of fully paid and nonassessable Zillow Group Class A common stock. Shares of Trulia common stock held by Trulia as treasury stock or by Zillow Group, Zillow, or any direct or indirect wholly owned subsidiary of Zillow or Trulia (“Trulia excluded shares”) were canceled and did not receive the Trulia merger consideration. Generally, each Trulia stock option, restricted stock unit, and stock appreciation right outstanding (whether or not vested or exercisable) as of the effective time of the Trulia Merger was assumed by Zillow Group and converted into a corresponding equity award to purchase, acquire shares of, or participate in the appreciation in price of Zillow Group Class A common stock, subject to the same terms, conditions and restrictions as the original option or award, subject to specified adjustments to reflect the effect of the Trulia exchange ratio. Each outstanding unvested Trulia stock option and restricted stock unit held by a member of the Trulia board of directors immediately prior to the effective time of the Trulia Merger who was not an employee of Trulia or any subsidiary of Trulia became fully vested immediately prior to the effective time of the Trulia Merger in accordance with the terms of the applicable award agreements. Our acquisition of Trulia has been accounted for as a business combination, and assets acquired and liabilities assumed were recorded at their estimated fair values as of February 17, 2015. Goodwill, which represents the expected synergies from combining the acquired assets and the operations of the acquirer, as well as intangible assets that do not qualify for separate recognition, is measured as of the acquisition date as the excess of consideration transferred, which is also measured at fair value, and the net of the fair values of the assets acquired and the liabilities assumed as of the acquisition date. In all cases in which Zillow Group’s closing stock price is a determining factor in arriving at the amount of merger consideration, the stock price assumed is the closing price of Zillow Class A common stock on NASDAQ on February 17, 2015 ($109.14 per share, unadjusted for the August 2015 stock split effected in the form of a dividend). The purchase price to effect the acquisition of Trulia of approximately $2.0 billion is summarized in the following table (in thousands): Value of Class A Common stock issued $ 1,883,728 Substituted stock options and stock appreciation rights attributable to pre-combination service 54,853 Substituted restricted stock units attributable to pre-combination service 27,798 Cash paid in lieu of fractional outstanding shares 41 Total purchase price $ 1,966,420 A total of 17,259,704 shares of Zillow Group Class A common stock were issued in connection with the acquisition of Trulia. Trulia stockholders did not receive any fractional shares of Zillow Group Class A common stock in connection with the acquisition. Instead of receiving any fractional shares, each holder of Trulia common stock was paid an amount in cash (without interest) equal to such fractional amount multiplied by the last reported sale price of Zillow Class A common stock on NASDAQ on the last complete trading day prior to the date of the effective time of the Trulia Merger. A portion of the purchase price has been attributed to the substitution of Trulia’s stock options, restricted stock units and stock appreciation rights outstanding as of February 17, 2015, for corresponding stock options, restricted stock units and stock appreciation rights to purchase, vest in or participate in the appreciation in price of shares of Zillow Group Class A common stock, all at an exchange ratio of 0.444. The fair value of Trulia’s share-based awards assumed in connection with the acquisition, including stock options, restricted stock units and stock appreciation rights, which relate to post-combination service will be recorded by Zillow Group as share-based compensation expense ratably over the remaining related vesting period of the respective award. The share-based compensation expense related to stock options and stock appreciation rights assumed is estimated at the acquisition date using the Black-Scholes-Merton option-pricing model, assuming no dividends, expected volatility of 53%, a risk-free interest rate of 1.10%, and an expected life of three years. For restricted stock units assumed, Zillow Group used the market value of Zillow’s Class A common stock on the date of acquisition to determine the fair value of the award. The total purchase price has been allocated to the assets acquired and liabilities assumed, including identifiable intangible assets, based on their respective fair values at the acquisition date. Based upon the fair values determined by us, in which we considered or relied in part upon a valuation report of a third-party expert, the total purchase price was allocated as follows (in thousands): Cash and cash equivalents $ 173,447 Accounts receivable 13,093 Prepaid expenses and other current assets 20,833 Restricted cash 6,946 Property and equipment 30,189 Other assets 434 Identifiable intangible assets 549,000 Goodwill 1,736,362 Accounts payable, accrued expenses and other current liabilities (51,258 ) Accrued compensation and benefits (8,324 ) Deferred revenue (8,300 ) Long-term debt (230,000 ) Debt premium recorded in additional paid-in capital (126,386 ) Deferred tax liabilities and other long-term liabilities (139,616 ) Total preliminary estimated purchase price $ 1,966,420 The preliminary estimated fair value of identifiable intangible assets acquired consisted of the following (in thousands): Preliminary Fair Value Estimated Useful Life (in years) Trulia trade names and trademarks $ 351,000 Indefinite Market Leader trade names and trademarks 2,000 2 Customer relationships 92,000 3-7 Developed technology 91,000 3-7 Advertising relationships 9,000 3 MLS home data feeds 4,000 3 Total $ 549,000 The preliminary estimated fair value of the intangible assets acquired was determined by Zillow Group, and Zillow Group considered or relied in part upon a valuation report of a third-party expert. Zillow Group used an income approach to measure the fair value of the trade names and trademarks and the developed technology based on the relief-from-royalty method. Zillow Group used an income approach to measure the fair value of the customer relationships based on the excess earnings method, whereby the fair value is estimated based upon the present value of cash flows that the applicable asset is expected to generate. Zillow Group used an income approach to measure the fair value of the advertising relationships based on a with and without analysis, whereby the fair value is estimated based on the present value of cash flows the combined business is expected to generate with and without the advertising relationships. Zillow Group used a cost approach to measure the fair value of the MLS home data feeds based on the estimated cost to replace the data feed library. These fair value measurements were based on Level 3 measurements under the fair value hierarchy. A portion of the total purchase price was allocated to Trulia’s 2020 Notes (see Note 12). In accordance with the accounting guidance related to business combinations, the 2020 Notes are recognized at fair value as of the effective date of the acquisition. The preliminary estimated fair value of the 2020 Notes is approximately $356.4 million. The preliminary estimated fair value of the 2020 Notes as of the date of acquisition was determined by Zillow Group, and Zillow Group considered or relied in part upon a valuation report of a third-party expert. The preliminary estimated fair value of the 2020 Notes was determined through combination of the use of a binomial lattice valuation model and consideration of quoted market prices. The fair value is classified as Level 3 due to the use of significant unobservable inputs such as implied volatility of Zillow Group’s Class A common stock, discount spread and the limited trading activity for the 2020 Notes. Given the preliminary fair value of the 2020 Notes of $356.4 million is at a substantial premium to the principal amount of $230.0 million, the premium amount of $126.4 million has been recorded as additional paid-in capital in the consolidated balance sheet as of the effective date of the acquisition. Accordingly, Zillow Group has recognized the liability component of the 2020 Notes at the stated par amount in the consolidated balance sheet as of the effective date of the acquisition. The conversion feature included in the 2020 Notes is not required to be bifurcated and separately accounted for as it meets the equity scope exception given the conversion feature (i) is indexed to Zillow Group’s Class A common stock and (ii) would be classified in shareholder’s equity. Further, the 2020 Notes do not permit or require Zillow Group to settle the debt in cash (in whole or in part) upon conversion. A portion of the total purchase price was allocated to deferred tax liabilities primarily related to an indefinite-lived intangible asset generated in connection with the acquisition. Due to the recognition of a $351.0 million indefinite-lived Trulia trade name and trademark intangible asset as of the effective date of the acquisition, a deferred tax liability of $139.5 million is recognized which cannot be offset by the recognized deferred tax assets. Our estimates and assumptions related to the purchase price allocation are preliminary and subject to change during the measurement period (up to one year from the acquisition date) as we finalize the amount of intangible assets, goodwill, and deferred taxes recorded in connection with the acquisition. The results of operations related to the acquisition of Trulia have been included in our consolidated financial statements since the date of acquisition of February 17, 2015. However, disclosure of the amounts of revenue and earnings of the acquiree since the acquisition date is impracticable because discrete financial information is not available due to the rapid integration of Zillow’s and Trulia’s operations. Unaudited Pro Forma Financial Information The following unaudited pro forma condensed combined financial information gives effect to the acquisition of Trulia as if it were consummated on January 1, 2014 (the beginning of the comparable prior reporting period). The unaudited pro forma condensed combined financial information is presented for informational purposes only. The unaudited pro forma condensed combined financial information does not represent true historical financial information. Further, the unaudited pro forma condensed combined financial information is not intended to represent or be indicative of the results of operations that would have been reported had the acquisition occurred on January 1, 2014 and should not be taken as representative of future results of operations of the combined company. The following table presents the unaudited pro forma condensed combined financial information for the periods presented (in thousands): Year Ended December 31, 2015 (1) 2014 (2) Revenue $ 679,935 $ 577,830 Net loss $ (91,055 ) $ (83,336 ) (1) The year ended December 31, 2015 includes pro forma adjustments for $49.3 million to eliminate direct and incremental acquisition-related costs reflected in the historical financial statements, $37.3 million to eliminate share-based compensation expense attributable to substituted equity awards and to record additional share-based compensation expense attributable to substituted equity awards, $35.7 million to eliminate restructuring costs associated with the acquisition of Trulia reflected in the historical financial statements and $2.4 million to record additional amortization expense for acquired intangible assets. (2) The year ended December 31, 2014 includes pro forma adjustments for $39.5 million to eliminate direct and incremental acquisition-related costs reflected in the historical financial statements, $18.7 million to record additional amortization expense for acquired intangible assets, $10.7 million to eliminate share-based compensation expense attributable to substituted equity awards, $6.2 million to eliminate Trulia’s historical amortization of capitalized website development costs and $2.7 million to record additional rent expense. Acquisition of DotLoop In July 2015, Zillow, Inc., Delta MergerCo, Inc., a Delaware corporation and wholly owned subsidiary of Zillow, Inc. (“Merger Sub”), DotLoop, a Delaware corporation, and Fortis Advisors, LLC, a Delaware limited liability company acting as the stockholder representative, entered into an Agreement and Plan of Merger (the “DotLoop Merger Agreement”), pursuant to which Zillow, Inc. acquired DotLoop on August 20, 2015. Under the terms and subject to the conditions of the DotLoop Merger Agreement, Merger Sub merged with and into DotLoop, with DotLoop remaining as the surviving company and a wholly owned subsidiary of Zillow, Inc. (the “DotLoop Merger”). DotLoop simplifies multi-party real estate transactions by enabling real estate professionals and their clients to share, edit, sign, and store documents digitally. Our acquisition of DotLoop has been accounted for as a business combination, and assets acquired and liabilities assumed were recorded at their estimated fair values as of August 20, 2015. Goodwill, which represents the expected synergies from combining the acquired assets and the operations of the acquirer, as well as intangible assets that do not qualify for separate recognition, is measured as of the acquisition date as the excess of consideration transferred, which is also measured at fair value, and the net of the fair values of the assets acquired and the liabilities assumed as of the acquisition date. The purchase price to effect the acquisition of DotLoop of approximately $105.5 million is summarized in the following table (in thousands): Cash paid for the outstanding stock and warrants of DotLoop $ 94,957 Cash paid for the cancellation of vested options to purchase shares of DotLoop’s common stock 5,640 Certain transaction expenses and other costs incurred by DotLoop 4,750 Substituted stock options attributable to pre-combination service 191 Total purchase price $ 105,538 A portion of the purchase price has been attributed to the substitution of DotLoop’s unvested stock options outstanding as of August 20, 2015, for corresponding stock options to purchase shares of Zillow Group Class C capital stock at an exchange ratio implied by the merger consideration. The fair value of DotLoop’s unvested stock options substituted in connection with the acquisition which relate to post-combination service will be recorded by Zillow Group as share-based compensation expense ratably over the remaining related vesting period of the respective award. The share-based compensation expense related to unvested stock options substituted is estimated at the acquisition date using the Black-Scholes-Merton option-pricing model, assuming no dividends, expected volatility of 55%, a risk-free interest rate of 1.25%, and an expected life of 4.28 years. The total purchase price has been allocated to the assets acquired and liabilities assumed, including identifiable intangible assets, based on their respective fair values at the acquisition date. Based upon the fair values determined by us, in which we considered or relied in part upon a valuation report of a third-party expert, the total purchase price was allocated as follows (in thousands): Cash, cash equivalents, accounts receivable, prepaid expenses and other current assets $ 2,149 Property and equipment and other assets 258 Identifiable intangible assets 22,500 Goodwill 86,128 Accounts payable, accrued expenses and other current liabilities, accrued compensation and benefits, and deferred revenue (1,362 ) Deferred tax liabilities (4,135 ) Total preliminary estimated purchase price $ 105,538 The preliminary estimated fair value of identifiable intangible assets acquired consisted of the following (in thousands): Preliminary Fair Value Estimated Useful Life (in years) Developed technology $ 10,700 3 Customer relationships 10,200 6-7 Trade names and trademarks 1,600 3 Total $ 22,500 The preliminary estimated fair value of the intangible assets acquired was determined by Zillow Group, and Zillow Group considered or relied in part upon a valuation report of a third-party expert. Zillow Group used an income approach to measure the fair value of the developed technology and the trade names and trademarks based on the relief-from-royalty method. Zillow Group used an income approach to measure the fair value of the customer relationships based on the excess earnings method, whereby the fair value is estimated based upon the present value of cash flows that the applicable asset is expected to generate. These fair value measurements were based on Level 3 measurements under the fair value hierarchy. Our estimates and assumptions related to the purchase price allocation are preliminary and subject to change during the measurement period (up to one year from the acquisition date) as we finalize the amount of intangible assets, goodwill and deferred taxes recorded in connection with the acquisition. Acquisition-related costs incurred, which primarily included legal and accounting fees and other external costs directly related to the acquisition, were expensed as incurred and were not material. The results of operations related to the acquisition of DotLoop have been included in our consolidated financial statements since the date of acquisition, and are not significant. Pro forma financial information for the acquisition accounted for as a business combination has not been presented, as the effects were not material to our consolidated financial statements.

Divestiture of Market Leader

Divestiture of Market Leader	12 Months Ended
	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Divestiture of Market Leader	Note 8. Divestiture of Market Leader On September 2, 2015, Zillow Group, Market Leader, Inc., an indirect wholly-owned subsidiary of Zillow Group (“ML, Inc.”), Market Leader, LLC d/b/a Market Leader, LLC of Nevada, an indirect wholly-owned subsidiary of Zillow Group (together with ML, Inc., “Market Leader”), Constellation Homebuilder Systems, Corp. (“Constellation Canada”) and Constellation Web Solutions Inc. (together with Constellation Canada, the Perseus Division of Constellation), entered into an Asset Purchase Agreement (the “Asset Purchase Agreement”) pursuant to which Constellation acquired Zillow Group’s Market Leader business, including the Sharper Agent service and the Leads Direct, HouseValues and JustListed lead generation businesses, on September 30, 2015. Market Leader became part of Zillow Group through Zillow Group’s February 2015 acquisition of Trulia. Constellation acquired substantially all of the assets of the Market Leader business and assumed certain related liabilities, including Zillow Group’s Bellevue, Washington operating lease (see Note 17). In connection with the divestiture, Market Leader’s approximately 100 employees transferred with the business to Constellation. The total sale price of approximately $22.6 million includes $17.0 million that was paid in cash at closing and approximately $5.6 million for the amount received by Zillow Group from Constellation on December 29, 2015 upon the expiration of a holdback period to satisfy any purchase price adjustments and/or certain indemnification claims. The following table presents the aggregate carrying amounts of the major classes of assets and liabilities related to the Market Leader disposal group as of the date of divestiture of September 30, 2015 (in thousands): Assets Prepaid expenses and other current assets $ 501 Property and equipment, net 5,764 Goodwill 9,209 Intangible assets, net 17,161 Total assets $ 32,635 Liabilities Current liabilities $ 2,278 Other long-term liabilities 3,771 Total liabilities $ 6,049 The total loss recorded related to the divestiture of Market Leader was $4.4 million for the year ended December 31, 2015 and is included in loss on divesture of business in our consolidated statements of operations. In July 2015, we determined that Market Leader met the held for sale criteria. The operating results of Market Leader prior to the date of divestiture have not been presented as discontinued operations in our consolidated statements of operations, as the disposal group does not represent a strategic shift in our operations or financial results.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Note 9. Goodwill The following table presents the change in goodwill from December 31, 2014 through December 31, 2015 (in thousands): Balance as of December 31, 2014 $ 96,352 Goodwill recorded in connection with the acquisition of Trulia 1,736,362 Goodwill recorded in connection with the acquisition of DotLoop 86,128 Reduction of goodwill in connection with the divestitures of businesses (9,675 ) Balance as of December 31, 2015 $ 1,909,167 The goodwill recorded in connection with the February 2015 acquisition of Trulia, which is not deductible for tax purposes, includes intangible assets that do not qualify for separate recognition, such as the assembled workforce and anticipated synergies from complementary products, and largely non-overlapping customer bases. The goodwill recorded in connection with the acquisition of DotLoop, which includes intangible assets that do not qualify for separate recognition, is not deductible for tax purposes.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Note 10. Intangible Assets The following tables present the detail of intangible assets subject to amortization as of the dates presented (in thousands): December 31, 2015 Cost Accumulated Net Purchased content $ 37,581 $ (19,649 ) $ 17,932 Customer relationships 103,425 (16,204 ) 87,221 Developed technology 108,295 (19,515 ) 88,780 Trade names and trademarks 4,860 (2,212 ) 2,648 Advertising relationships 9,000 (2,598 ) 6,402 MLS home data feeds 1,100 (318 ) 782 Total $ 264,261 $ (60,496 ) $ 203,765 December 31, 2014 Cost Accumulated Net Purchased content $ 24,615 $ (13,904 ) $ 10,711 Developed technology 13,595 (5,321 ) 8,274 Customer relationships 9,225 (3,387 ) 5,838 Trademarks 3,261 (1,327 ) 1,934 Total $ 50,696 $ (23,939 ) $ 26,757 Amortization expense recorded for intangible assets for the years ended December 31, 2015, 2014 and 2013 was $39.3 million, $11.1 million and $7.6 million, respectively, and these amounts are included in technology and development expenses. Estimated future amortization expense for intangible assets, including amortization related to future commitments (see Note 17), as of December 31, 2015 is as follows (in thousands): 2016 $ 46,377 2017 44,090 2018 37,727 2019 32,906 2020 32,415 All future years 43,894 Total future amortization expense $ 237,409 As of December 31, 2015, we have an indefinite-lived intangible asset for $351.0 million that we recorded in connection with our February 2015 acquisition of Trulia for Trulia’s trade names and trademarks that is not subject to amortization. See Note 7 for further details related to the acquisition.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Note 11. Accrued Expenses and Other Current Liabilities The following table presents the detail of accrued expenses and other current liabilities as of as of the dates presented (in thousands): December 31, 2015 2014 Accrued marketing and advertising $ 9,663 $ 1,509 Accrued purchased content 8,385 — Accrued legal fees 7,784 3,755 Merger consideration payable to former stockholders of StreetEasy, Inc. 5,317 5,317 Other accrued expenses and other current liabilities 11,898 6,302 Total accrued expenses and other current liabilities $ 43,047 $ 16,883

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Convertible Senior Notes	Note 12. Convertible Senior Notes In connection with the February 2015 acquisition of Trulia (see Note 7), a portion of the total purchase price was allocated to Trulia’s Convertible Senior Notes due in 2020 (the “2020 Notes”), which are unsecured senior obligations. Pursuant to and in accordance with the Merger Agreement, Zillow Group entered into a supplemental indenture in respect of the 2020 Notes in the aggregate principal amount of $230.0 million, which supplemental indenture provides, among other things, that, at the effective time of the Trulia Merger, (i) each outstanding 2020 Note is no longer convertible into shares of Trulia common stock and is convertible solely into shares of Zillow Group Class A common stock, pursuant to, and in accordance with, the terms of the indenture governing the 2020 Notes, and (ii) Zillow Group guaranteed all of the obligations of Trulia under the 2020 Notes and related indenture. The aggregate principal amount of the 2020 Notes is due on December 15, 2020 if not earlier converted or redeemed. Interest is payable on the 2020 Notes at the rate of 2.75% semi-annually on June 15 and December 15 of each year. Holders of the 2020 Notes may convert all or any portion of their notes, in multiples of $1,000 principal amount, at their option at any time prior to the close of business on the business day immediately preceding the maturity date. In connection with the supplemental indenture in respect of the 2020 Notes, the conversion ratio immediately prior to the effective time of the Trulia Merger of 27.8303 shares of Trulia common stock per $1,000 principal amount of notes was adjusted to 12.3567 shares of our Class A common stock per $1,000 principal amount of notes based on the exchange ratio of 0.444 per the Merger Agreement. This was equivalent to an initial conversion price of approximately $80.93 per share of our Class A common stock. In connection with the Class C Stock Split described below under Note 14, the conversion ratio has been further adjusted to 41.4550 shares of Class A common stock per $1,000 principal amount of notes, which is equivalent to a conversion price of approximately $24.12 per share of our Class A common stock. The conversion ratio will be adjusted for certain dilutive events and will be increased in the case of corporate events that constitute a “Make-Whole Fundamental Change” (as defined in the indenture governing the notes). The conversion option of the 2020 Notes has no cash settlement provisions. The conversion option does not meet the criteria for separate accounting as a derivative as it is indexed to our own stock. The holders of the 2020 Notes will have the ability to require us to repurchase the notes in whole or in part upon the occurrence of an event that constitutes a “Fundamental Change” (as defined in the indenture governing the notes, including such events as a “change in control” or “termination of trading”, subject to certain exceptions). In such case, the repurchase price would be 100% of the principal amount of the 2020 Notes plus accrued and unpaid interest, if any, to, but excluding, the Fundamental Change repurchase date. Certain events are also considered “Events of Default,” which may result in the acceleration of the maturity of the 2020 Notes, as described in the indenture governing the notes. There are no financial covenants associated with the 2020 Notes. We may not redeem the 2020 Notes prior to December 20, 2018. We may redeem the 2020 Notes, at our option, in whole or in part on or after December 20, 2018, if the last reported sale price per share of our Class A common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period. Interest expense related to the 2020 Notes for the year ended December 31, 2015 was $5.5 million. Accrued interest related to the 2020 Notes as of December 31, 2015 is $0.3 million, and is recorded in accrued expenses and other current liabilities in our consolidated balance sheet. The estimated fair value and carrying value of the 2020 Notes were $272.9 million and $230.0 million, respectively, as of December 31, 2015. The estimated fair value of the 2020 Notes was determined through consideration of quoted market prices. The fair value is classified as Level 3 due to the limited trading activity for the 2020 Notes.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Note 13. Income Taxes We are subject to federal and state income taxes in the United States and in Canada. For the years ended December 31, 2015, 2014 and 2013, we did not have a material amount of reportable taxable income and, therefore, no related tax liability or expense has been recorded in the consolidated financial statements. We recorded an income tax benefit of $4.6 million for the year ended December 31, 2015 primarily due to a deferred tax liability generated in connection with Zillow Group’s August 20, 2015 acquisition of DotLoop that can be used to realize certain deferred tax assets for which we had previously provided a full allowance. We recorded an income tax benefit of $4.1 million for the year ended December 31, 2013 due to a deferred tax liability generated in connection with Zillow’s August 26, 2013 acquisition of StreetEasy, Inc. that can be used to realize certain deferred tax assets for which we had previously provided a full valuation allowance. The following table summarizes the components of our income tax benefit for the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Federal $ 2,838 $ — $ 3,783 State 1,807 — 328 Deferred income tax benefit $ 4,645 $ — $ 4,111 The following table presents a reconciliation of the federal statutory rate and our effective tax rate for the periods presented: Year Ended December 31, 2015 2014 2013 Tax expense at federal statutory rate (35.0 )% (34.0 )% (34.0 )% State income taxes, net of federal tax benefit (2.3 )% (1.5 )% (5.8 )% Nondeductible expenses 2.8 % 15.3 % 3.1 % Share-based compensation 1.2 % 0.7 % 0.2 % Research and development credits (4.1 )% (3.2 )% (23.3 )% Divestiture of businesses 2.3 % — — Other (1.0 )% — — Valuation allowance 33.1 % 22.7 % 35.0 % Effective tax rate (3.0 )% 0.0 % (24.8 )% Deferred federal, state and foreign income taxes reflect the net tax impact of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and such amounts for tax purposes. The following table presents the significant components of our deferred tax assets and liabilities as of the dates presented (in thousands): December 31, 2015 2014 Deferred tax assets: Federal and state net operating loss carryforwards $ 162,521 $ 25,665 Share-based compensation 45,969 12,680 Goodwill 825 1,355 Depreciation and amortization 3,090 — Start-up and organizational costs 369 430 Research and development credits 21,157 6,493 Other tax credits 1,358 — Accruals and reserves 3,338 2,339 Deferred rent 5,228 4,248 Other deferred tax assets 550 167 Total deferred tax assets 244,405 53,377 Deferred tax liabilities: Website and software development costs (13,851 ) (7,263 ) Intangibles (200,082 ) (6,052 ) Other deferred tax liabilities (52 ) — Depreciation and amortization — (2,838 ) Net deferred tax assets before valuation allowance 30,420 37,224 Less: valuation allowance (162,715 ) (37,224 ) Net deferred tax assets (liabilities) $ (132,295 ) $ — Realization of deferred tax assets is dependent upon the generation of future taxable income, if any, the timing and amount of which are uncertain. We have provided a full valuation allowance against the net deferred tax assets as of December 31, 2015 and 2014 because, 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 will not be realized. The valuation allowance increased by $125.5 million and $9.9 million, respectively, during the years ended December 31, 2015 and 2014. We have accumulated federal tax losses of approximately $735.2 million and $358.6 million, respectively, as of December 31, 2015 and 2014, which are available to reduce future taxable income. We have accumulated state tax losses of approximately $11.6 million and $7.2 million (tax effected), respectively, as of December 31, 2015 and 2014. As of December 31, 2015, approximately $304.0 million of our net operating loss carryforwards relate to tax deductible share-based compensation in excess of amounts recognized for financial reporting purposes. To the extent that net operating loss carryforwards, if realized, relate to share-based compensation, the resulting tax benefits will be recorded to shareholders’ equity rather than to the statement of operations. Additionally, we have net research and development credit carryforwards of $17.2 million and $6.5 million, respectively, as of December 31, 2015 and 2014, which are available to reduce future tax liabilities. The tax loss and research and development credit carryforwards begin to expire in 2025. Under Sections 382 and 383 of the Internal Revenue Code, if a corporation undergoes an ownership change, the corporation’s ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes, such as research tax credits, to offset its post-change income or income tax liability may be limited. In connection with our August 2013 public offering of our Class A Common stock, we experienced an ownership change that triggered Sections 382 and 383, which may limit our ability to utilize net operating loss and tax credit carryforwards. In connection with Zillow Group’s February 2015 acquisition of Trulia, Trulia experienced an ownership change that triggered Section 382 and 383, which may limit Zillow Group’s ability to utilize Trulia’s net operating loss and tax credit carryforwards. We are currently not under audit in any tax jurisdiction. Tax years from 2012 through 2015 are currently open for audit by federal and state taxing authorities. Changes for unrecognized tax benefits for the periods presented are as follows (in thousands): Balance at January 1, 2013 $ 1,255 Gross increases—prior and current period tax positions 3,868 Balance at December 31, 2013 $ 5,123 Gross increases—current period tax positions 1,946 Gross decreases—prior period tax positions (576 ) Balance at December 31, 2014 $ 6,493 Gross increases—prior and current period tax positions 3,577 Gross increases—assumed in connection with February 2015 acquisition of Trulia 3,910 Balance at December 31, 2015 $ 13,980 At December 31, 2015, the total amount of unrecognized tax benefits of $14.0 million is recorded as a reduction to the deferred tax asset. We do not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease within the next 12 months. Accrued interest and penalties related to unrecognized tax benefits are recorded as income tax expense and are zero.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Shareholders' Equity	Note 14. Shareholders’ Equity Preferred Stock Our board of directors has the authority to fix and determine and to amend the number of shares of any series of preferred stock that is wholly unissued or to be established and to fix and determine and to amend the designation, preferences, voting powers and limitations, and the relative, participating, optional or other rights, of any series of shares of preferred stock that is wholly unissued or to be established, subject in each case to certain approval rights of holders of our outstanding Class B common stock. There was no preferred stock issued and outstanding as of December 31, 2015 or December 31, 2014. Common and Capital Stock Our Class A common stock has no preferences or privileges and is not redeemable. Holders of Class A common stock are entitled to one vote for each share. Our Class B common stock has no preferences or privileges and is not redeemable. At any time after the date of issuance, each share of Class B common stock, at the option of the holder, may be converted into one share of Class A common stock, or automatically converted into Class A common stock upon the affirmative vote by or written consent of holders of a majority of the shares of the Class B common stock. During the years ended December 31, 2015, 2014, and 2013, no shares, 251,445 shares, and 993,634 shares, respectively of Class B common stock were converted into Class A common stock at the option of the holders. Holders of Class B common stock are entitled to 10 votes for each share. Our Class C capital stock has no preferences or privileges, is not redeemable and, except in limited circumstances, is non-voting. In August 2013, we sold 3,253,522 shares of our Class A common stock, including 753,522 shares of our Class A common stock pursuant to the underwriters’ option to purchase additional shares, and certain shareholders sold 2,523,486 shares of our Class A common stock, at a price of $82.00 per share (unadjusted for the August 2015 stock split effected in the form of a dividend). We received net proceeds of $253.9 million after deducting underwriting discounts and commissions and offering expenses payable by us. We received no proceeds from the sale of our Class A common stock by the selling shareholders. The following shares of common and capital stock have been reserved for future issuance as of the dates presented, and share numbers as of December 31, 2014 have been retroactively adjusted to reflect the effects of the Class C Stock Split defined below: December 31, December 31, Option awards outstanding 27,126,374 17,399,292 Restricted stock units outstanding 2,605,514 376,806 Class A common stock and Class C capital stock available for grant under 2011 Plan 688,014 2,017,818 Shares issuable upon conversion of outstanding Class B common stock 6,217,447 6,217,447 Total 36,637,349 26,011,363 Stock Split Effected in Form of Stock Dividend In December 2014 and in connection with the Trulia acquisition, the shareholders of Zillow and the stockholders of Trulia approved amendments to Zillow Group’s amended and restated articles of incorporation to, among other things, create a new class of non-voting Class C capital stock. On July 21, 2015, we announced that our board of directors had approved a distribution of shares of our Class C capital stock as a dividend to our Class A and Class B common shareholders (the “Class C Stock Split”). Holders of Class A common stock and Class B common stock as of the close of business on July 31, 2015, the record date for the Class C Stock Split, received on August 14, 2015 a distribution of two shares of Class C capital stock for each share of Class A and Class B common stock held by them as of the record date. The distribution of shares had the effect of a 3-for-1 stock split. Outstanding equity awards to purchase or acquire shares of Class A common stock were proportionately adjusted to relate to one share of Class A common stock and two shares of Class C capital stock for each share of Class A common stock subject to the awards as of the record date, and the exercise prices of any such awards were also proportionately allocated between Class A common stock and Class C capital stock. The adjustment to outstanding equity awards resulted in an immaterial amount of incremental aggregate fair value associated with the awards outstanding immediately following the Class C Stock Split as compared to just prior to the Class C Stock Split, which did not have a material impact on our consolidated statements of operations for the periods presented. The par value per share of our shares of Class A common stock and Class B common stock have remained unchanged at $0.0001 per share after the Class C Stock Split. On the effective date of the Class C Stock Split, we transferred between additional paid in capital and Class C capital stock an amount equal to the $0.0001 par value of the Class C capital stock that was issued. We have given retroactive effect to prior period share and per share amounts in our consolidated financial statements for the effect of the Class C Stock Split so that prior periods are comparable to current period presentation.

Share-Based Awards

Share-Based Awards	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Awards	Note 15. Share-Based Awards In connection with our February 2015 acquisition of Trulia, we assumed the obligations of Zillow, Trulia and Market Leader outstanding under pre-existing stock plans. In addition, we assumed the Zillow 2011 Incentive Plan, as amended and/or restated, and the Trulia 2012 Equity Incentive Plan, as amended and restated, for purposes of future grants, with the number and type of shares issuable thereunder appropriately adjusted to reflect the acquisition in accordance with applicable NASDAQ exchange listing requirements. In connection with the Class C Stock Split discussed in Note 14 above, all outstanding equity awards under each of the plans described below (collectively, the “Plans”) as of the record date were proportionately adjusted to relate to one share of Class A common stock and two shares of Class C capital stock for each share of Class A common stock subject to the awards as of the record date (the “Split Adjustment”). The original exercise prices of outstanding stock options and stock appreciation rights were proportionally allocated between shares of Class A common stock and Class C capital stock, based on the ratio of the when-issued trading prices of the Class A common stock and the Class C capital stock during the ten trading days prior to and including the payment date of the Class C Stock Split. In connection with the Split Adjustment, each stock option and stock appreciation right is independently exercisable (to the extent vested) for shares of Class A common stock and shares of Class C capital stock so that, in effect, for each share of Class A common stock subject to the option or stock appreciation right prior to the Class C Stock Split, the Split Adjustment resulted in a stock option to purchase one share of Class A common stock and a stock option to purchase two shares of Class C capital stock. Each such adjusted equity award otherwise has the same terms and conditions, including the vesting schedule and term, as the original equity award prior to the Split Adjustment. Zillow Group, Inc. Amended and Restated 2011 Incentive Plan On July 19, 2011, Zillow’s 2011 Incentive Plan (as amended and/or restated from time to time, the “2011 Plan”) became effective and serves as the successor to Zillow’s 2005 Equity Incentive Plan (the “2005 Plan”). Effective June 11, 2015, the 2011 Plan was amended and restated as the Zillow Group, Inc. Amended and Restated 2011 Incentive Plan to, among other changes: (i) increase the number of shares authorized for issuance by 1,500,000 shares, from 3,800,000 shares to 5,300,000 shares; (ii) introduce flexibility to grant Class C capital stock, in addition to or in lieu of, Class A common stock under the 2011 Plan (references in this discussion to “common stock” under the 2011 Plan generally refer to both Class A common stock and Class C capital stock); and (iii) update references to “Zillow, Inc.” to “Zillow Group, Inc.” as applicable. Shareholders approved the amended and restated 2011 Plan on June 11, 2015, and we intend that future equity grants will be made under this plan only (or a successor thereto). As a result of the Class C Stock Split, the number of shares available for future awards under the 2011 Plan was adjusted by 1,953,950 shares, which were registered as Class C capital stock. The 2011 Plan provides that in the event of a stock dividend, stock split or similar event, the maximum number and kind of securities available for issuance under the plan will be proportionally adjusted. Under the 2011 Plan, 15,900,000 shares of common stock (as adjusted in connection with the Class C Stock Split) (or 5,300,000 shares of common stock before the Class C Stock Split took effect on August 14, 2015) are reserved for issuance. The number of shares of common stock available for issuance under the 2011 Plan automatically increases on the first day of each of our fiscal years beginning in 2016 by a number of shares equal to the least of (a) 3.5% of our outstanding common stock on a fully diluted basis as of the end of our immediately preceding fiscal year, (b) 10,500,000 shares (or 3,500,000 shares before the Class C Stock Split took effect on August 14, 2015), and (c) a lesser amount determined by our board of directors; provided, however, that any shares from any increases in previous years that are not actually issued will continue to be available for issuance under the 2011 Plan. In addition, shares previously available for grant under the 2005 Plan, but not issued or subject to outstanding awards under the 2005 Plan as of July 19, 2011, and shares subject to outstanding awards under the 2005 Plan that subsequently cease to be subject to such awards (other than by reason of exercise of the awards) are available for grant under the 2011 Plan. The 2011 Plan is administered by the compensation committee of the board of directors. Under the terms of the 2011 Plan, the compensation committee may grant equity awards, including incentive stock options, nonqualified stock options, restricted stock, restricted stock units or restricted units to employees, officers, directors, consultants, agents, advisors and independent contractors. The compensation committee has also authorized certain senior executive officers to grant equity awards under the 2011 Plan, within limits prescribed by the compensation committee. Options under the 2011 Plan are granted with an exercise price per share not less than 100% of the fair market value of our common stock on the date of grant, with the exception of substituted option awards granted in connection with acquisitions, and are exercisable at such times and under such conditions as determined by the compensation committee. Under the 2011 Plan, the maximum term of an option is ten years from the date of grant. Any portion of an option that is not vested and exercisable on the date of a participant’s termination of service expires on such date. Employees generally forfeit their rights to exercise vested options after 3 months following their termination of employment or 12 months in the event of termination by reason of death, disability or retirement. Options granted under the 2011 Plan are typically granted with seven-year terms and typically vest 25% after 12 months and ratably thereafter over the next 36 months, though certain options have been granted with longer terms and vesting schedules. Restricted stock units under the 2011 Plan typically vest either 25% after 12 months and quarterly thereafter over the next three years or 12.5% after 6 months and quarterly thereafter for the next 3.5 years. Any portion of a restricted stock unit that is not vested on the date of a participant’s termination of service expires on such date. Trulia 2005 Stock Incentive Plan Trulia granted options under the 2005 Stock Incentive Plan (as amended, “the 2005 Plan”) until September 2012 when the 2005 Plan was terminated. Stock options issued prior to the plan termination remained outstanding in accordance with their terms. Under the terms of the 2005 Plan, Trulia had the ability to grant incentive and nonqualified stock options, stock appreciation rights, restricted stock awards and restricted stock units. Options granted under the 2005 Plan generally vest at a rate of 25% after 12 months and ratably thereafter over the next 36 months and expire 10 years from the grant date. Certain options vest monthly over two to four years. Trulia 2012 Equity Incentive Plan, as Amended and Restated On September 19, 2012, Trulia’s 2012 Equity Incentive Plan (the “2012 Plan”) became effective. The 2012 Plan provides for the grant of incentive and nonqualified stock options, restricted stock, restricted stock units, stock appreciation rights, performance units and performance shares to employees, directors and consultants. Under the 2012 Plan, stock options are granted at a price per share not less than 100% of the fair market value per share of the underlying stock at the grant date. The plan administrator determines the vesting period for each option award on the grant date, and the options generally expire 10 years from the grant date or such shorter term as may be determined for the options. As noted above, we intend that future equity grants will be made under the 2011 Plan only. Market Leader Amended and Restated 2004 Equity Incentive Plan In connection with Trulia’s acquisition of Market Leader in 2013, Trulia assumed Market Leader’s Amended and Restated 2004 Equity Incentive Plan (the “2004 Plan”), including all outstanding shares of restricted stock, all outstanding stock appreciation rights, all outstanding options, and all shares available for future issuance under the 2004 Plan. Trulia granted equity awards, to the extent permissible by applicable law and New York Stock Exchange rules, under the 2004 Plan until it expired on December 9, 2014. The equity awards issued prior to the 2004 Plan’s expiration remained outstanding in accordance with their terms. Option Awards and Stock Appreciation Rights The following table summarizes option award and stock appreciation rights activity for the year ended December 31, 2015 and has been retroactively adjusted to reflect the effects of the Class C Stock Split: Number Weighted- Weighted- Aggregate (in thousands) Outstanding at January 1, 2015 17,399,292 $ 18.12 5.32 $ 311,040 Assumed Trulia options and stock appreciation rights in connection with February 2015 acquisition of Trulia 3,159,765 13.79 Granted 11,438,095 31.45 Exercised (2,732,767 ) 8.99 Forfeited or cancelled (2,138,011 ) 28.37 Outstanding at December 31, 2015 27,126,374 23.35 5.96 156,025 Vested and exercisable at December 31, 2015 9,470,685 14.44 3.93 112,923 The number of options granted during the year ended December 31, 2015 in the table above includes a total of 199,779 substituted options with a weighted-average exercise price of $9.29 per share granted in connection with our August 2015 acquisition of DotLoop. The fair value of options granted, excluding options granted under the Stock Option Grant Program for Nonemployee Directors (“Nonemployee Director Awards”) and certain options granted to the Company’s executives in January and February 2015 and January 2013, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model with the following assumptions for the periods presented: Year Ended December 31, 2015 2014 2013 Expected volatility 54% – 56% 53% – 57% 50% – 54% Expected dividend yield — — — Risk-free interest rate 1.03% – 1.48% 1.37% – 1.55% 0.70% – 1.27% Weighted-average expected life 3.50 – 4.58 years 4.58 years 4.58 years Weighted-average fair value of options granted $13.77 $14.78 $7.09 The weighted average estimated fair value of options granted included in the table above has been retroactively adjusted to reflect the effects of the Class C Stock Split. The assumptions included in the table above exclude Trulia’s stock options and stock appreciation rights assumed in connection with the February 17, 2015 acquisition and DotLoop’s unvested stock options substituted in connection with the August 20, 2015 acquisition (see Note 7). In January and February 2015, option awards for a total of 3,450,000 shares of Class A common stock and Class C capital stock (as adjusted in connection with the Class C Stock Split) were granted to certain of the Company’s executive officers. The fair value of the option awards is estimated at the date of grant using the Black-Scholes-Merton option-pricing model, assuming no dividends, expected volatility of 52%, a risk-free interest rate of 1.76% and a weighted-average expected life of 6.8 years. The grant date fair value of the option awards is approximately $62.8 million. One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the first anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable four years from the vesting commencement date. One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the two-year anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable five years from the vesting commencement date. One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the three-year anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable six years from the vesting commencement date. One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the four-year anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable seven years from the vesting commencement date. The option awards have a ten-year term. In March 2015, option awards for an aggregate of 47,175 shares of Class A common stock and Class C capital stock (as adjusted in connection with the Class C Stock Split) were granted as Nonemployee Director Awards, which are fully vested and exercisable on the date of grant. The fair value of options granted for the Nonemployee Director Awards, $15.90 per share, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model, assuming no dividends, expected volatility of 57%, a risk-free interest rate of 1.01%, and a weighted-average expected life of 3.5 years. During the year ended December 31, 2015, share-based compensation expense recognized in our statement of operations related to Nonemployee Director Awards was $0.8 million, and is included in general and administrative expenses. In January 2013, an option award for 1,500,000 shares of Class A common stock and Class C capital stock (as adjusted in connection with the Class C Stock Split) was granted to the Company’s chief executive officer. The fair value of the option award, $6.33 per share, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model, assuming no dividends, expected volatility of 51%, a risk-free interest rate of 0.70% and a weighted-average expected life of 7.3 years. As of December 31, 2015, there was a total of $203.9 million in unrecognized compensation cost related to unvested stock options and stock appreciation rights, which is expected to be recognized over a weighted-average period of 3.5 years. The total intrinsic value of options and stock appreciation rights exercised during the years ended December 31, 2015, 2014 and 2013 was $67.3 million, $124.0 million and $114.4 million, respectively. The fair value of options and stock appreciation rights vested for the years ended December 31, 2015, 2014 and 2013 was $59.9 million, $18.9 million and $10.6 million, respectively. Restricted Stock Awards The following table summarizes restricted stock award activity for the year ended December 31, 2015 and has been retroactively adjusted to reflect the effects of the Class C Stock Split: Shares of Weighted- Unvested outstanding at January 1, 2015 260,505 $ 10.75 Granted 4,173 40.45 Vested (233,732 ) 11.07 Forfeited or cancelled — — Unvested outstanding at December 31, 2015 30,946 12.35 The total fair value of shares of restricted stock awards vested for the years ended December 31, 2015, 2014 and 2013 was $2.6 million, $4.5 million and $3.4 million, respectively. The fair value of the outstanding restricted stock awards will be recorded as share-based compensation expense over the vesting period. As of December 31, 2015, there was $0.4 million of total unrecognized compensation cost related to restricted stock awards, which is expected to be recognized over a weighted-average period of 0.8 years. Restricted Stock Units The following table summarizes activity for restricted stock units for the year ended December 31, 2015 and has been retroactively adjusted to reflect the effects of the Class C Stock Split: Restricted Stock Units Weighted- Unvested outstanding at January 1, 2015 376,806 $ 28.56 Assumed Trulia restricted stock units in connection with February 2015 acquisition of Trulia 3,798,957 36.38 Granted 1,354,185 28.55 Vested (1,899,531 ) 31.74 Forfeited or cancelled (1,024,903 ) 31.12 Unvested outstanding at December 31, 2015 2,605,514 32.36 In February 2015, pursuant to the terms of a Restricted Stock Unit Award Notice and Restricted Stock Unit Award Agreement entered into between Zillow Group and an employee, Zillow Group granted to the employee restricted stock units for a total of 82,077 shares of Class A common stock and Class C capital stock (as adjusted in connection with the Class C Stock Split). For 50,202 of the restricted stock units, 25% of such restricted stock unit award will vest on February 17, 2016, and the remainder will vest in substantially equal installments each three-month period thereafter for three years, subject to the recipient’s continued full-time employment or service to Zillow Group. For 31,875 of the restricted stock units, one-eighth of such restricted stock unit award vested on August 17, 2015, and the remainder will vest in substantially equal installments each three-month period thereafter for three and a half years, subject to the recipient’s continued full-time employment or service to Zillow Group. In the event of termination of service or employment by Zillow Group without cause or upon the resignation by such employee for good reason, the employee will receive an additional 12 months’ accelerated vesting of the then outstanding restricted stock units, except that in the event of such a termination in connection with a change in control, the employee will receive 50% accelerated vesting of the then outstanding restricted stock units. The employee will be entitled to receive one share of Class A common stock and two shares of Class C capital stock for each then outstanding restricted stock unit that becomes vested. The grant date fair value of the restricted stock units is approximately $3.0 million. In April 2015, Zillow Group granted to certain employees supporting our Trulia brand retention restricted stock units for a total of 316,074 shares of Class A common stock and Class C capital stock (as adjusted in connection with the Class C Stock Split), of which 12.5% of the retention restricted stock units vested approximately 6 months after the vesting commencement date of February 18, 2015, and the remaining retention restricted stock units vest quarterly thereafter for approximately 3.5 years, subject to the recipient’s continued full-time employment or service to Zillow Group. The total grant date fair value of the retention restricted stock units is approximately $10.2 million. Pursuant to the terms of the DotLoop Merger Agreement, Zillow Group established a retention bonus plan in August 2015 pursuant to which a total of 178,428 restricted stock units for shares of our Class C capital stock have been granted to employees of DotLoop who accepted employment with Zillow Group, of which 25% of the restricted stock units vest on August 20, 2016, and the remaining restricted stock units vest quarterly thereafter over the next three years. The vesting of the restricted stock units is subject to the recipient’s continued full-time employment or service to Zillow Group. The total grant date fair value of the restricted stock units is approximately $4.5 million. In August 2015, pursuant to the terms of a Restricted Stock Unit Award Notice and Restricted Stock Unit Award Agreement between Zillow Group and an employee, Zillow Group granted to the employee 173,761 restricted stock units, of which 50% of the restricted stock units vest on August 21, 2016, and the remaining restricted stock units vest quarterly thereafter for the next three years. The vesting of the restricted stock units is subject to the recipient’s continued full-time employment or service to Zillow Group. The total grant date fair value of the restricted stock units is approximately $4.4 million. The total fair value of vested restricted stock units was $67.3 million, $5.1 million and $10.5 million, respectively, for the years ended December 31, 2015, 2014 and 2013. The fair value of the outstanding restricted stock units will be recorded as share-based compensation expense over the vesting period. As of December 31, 2015, there was $69.0 million of total unrecognized compensation cost related to restricted stock units, which is expected to be recognized over a weighted-average period of 2.6 years. Share-Based Compensation Expense The following table presents the effects of share-based compensation in our consolidated statements of operations during the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Cost of revenue $ 4,694 $ 1,844 $ 737 Sales and marketing 25,391 7,320 10,969 Technology and development 26,849 11,681 4,660 General and administrative 48,280 13,240 7,070 Restructuring costs 14,859 — — $ 120,073 $ 34,085 $ 23,436 Certain executives of Trulia are entitled to partial and/or full “double trigger” equity acceleration upon a termination without “cause” or a resignation for “good reason,” each within twelve months of the Trulia acquisition, pursuant to pre-existing offer letters and/or equity award agreements entered into with Trulia. For the year ended December 31, 2015, approximately $1.8 million, $1.4 million, and $6.7 million, respectively, of share-based compensation expense is included in sales and marketing expenses, technology and development expenses, and general and administrative expenses related to change in control equity acceleration for certain former executives of Trulia pursuant to Zillow Group’s February 2015 restructuring plan (see Note 18).

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss Per Share	Note 16. Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of shares (including Class A common stock, Class B common stock and Class C capital stock) outstanding during the period. In the calculation of basic net loss per share, undistributed earnings are allocated assuming all earnings during the period were distributed. Diluted net loss per share is computed by dividing net loss by the weighted-average number of shares (including Class A common stock, Class B common stock and Class C capital stock) outstanding during the period and potentially dilutive Class A common stock and Class C capital stock equivalents, except in cases where the effect of the Class A common stock or Class C capital stock equivalent would be antidilutive. Potential Class A common stock and Class C capital stock equivalents consist of Class A common stock and Class C capital stock issuable upon exercise of stock options and stock appreciation rights and Class A common stock and Class C capital stock underlying unvested restricted stock awards and unvested restricted stock units using the treasury stock method. Potential Class A common stock equivalents also include Class A common stock issuable upon conversion of the 2020 Notes using the if-converted method. For the periods presented, the following Class A common stock and Class C capital stock equivalents were excluded from the calculations of diluted net loss per share because their effect would have been antidilutive, which share numbers have been retroactively adjusted to reflect the effects of the Class C Stock Split (in thousands): Year Ended December 31, 2015 2014 2013 Class A common stock and Class C capital stock issuable upon the exercise of option awards and stock appreciation rights 6,751 8,709 9,537 Class A common stock and Class C capital stock underlying unvested restricted stock awards and restricted stock units 639 354 513 Class A common stock issuable upon conversion of the 2020 Notes 9,535 — — Total Class A common stock and Class C capital stock equivalents 16,925 9,063 10,050 In the event of liquidation, dissolution, distribution of assets or winding-up of the Company, the holders of all classes of common and capital stock have equal rights to receive all the assets of the Company after the rights of the holders of preferred stock have been satisfied. We have not presented net loss per share under the two-class method for our Class A common stock, Class B common stock and Class C capital stock because it would be the same for each class due to equal dividend and liquidation rights for each class.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 17. Commitments and Contingencies Lease Commitments We have various operating leases for office space and equipment. Seattle, Washington In March 2011, we entered into a lease agreement for office space that houses our corporate headquarters in Seattle (as amended from time to time, the “Seattle Lease”). Pursuant to the terms of the Seattle Lease, we currently occupy a total of 155,042 square feet, and we are obligated to make escalating monthly lease payments that began in December 2012 and continue through December 2024. In November 2014, we entered into a lease amendment under which we will lease an additional 113,470 square feet of office space. The Company has taken possession of a portion of the additional office space and will continue to take possession as space becomes available through 2017 under the same terms and conditions. San Francisco, California In connection with our February 2015 acquisition of Trulia, Inc. (“Trulia”), we assumed a lease agreement for office space in San Francisco (as amended from time to time, the “San Francisco Lease”), which houses Trulia’s corporate headquarters and beginning in March 2015, also houses Zillow’s personnel located in San Francisco. Pursuant to the terms of the San Francisco Lease, we lease a total of approximately 79,000 square feet, and we are obligated to make escalating monthly lease payments that began in November 2014 and continue through September 2023. In July 2014, Trulia entered into a lease amendment under which we lease an additional 26,620 square feet of office space under the same terms and conditions. In November 2012, we entered into an operating lease in San Francisco, California for 18,353 square feet under which we are obligated to make escalating monthly lease payments which began in December 2012 and continue through November 2018. In March 2015, we ceased use of this space in connection with our February 2015 acquisition of Trulia, and in May 2015, we sublet this office space to another occupant. Pursuant to the terms of the operating lease and since October 2015, we lease an additional 8,311 square feet of office space under the same terms and conditions. New York, New York In February 2014, we entered into an operating lease in New York (as amended from time to time, the “New York Lease”). Pursuant to the terms of the New York Lease, we lease a total of approximately 39,900 square feet, and we are obligated to make escalating monthly lease payments that began in August 2014 and continue through November 2024. In July 2015, we sublet approximately 6,650 square feet of this office space to another occupant. Denver, Colorado In connection with our February 2015 acquisition of Trulia, we assumed a lease agreement for office space in Denver. Pursuant to the terms of the lease, we lease a total of approximately 65,000 square feet, and we are obligated to make escalating monthly lease payments that began in November 2014 and continue through October 2021. Bellevue, Washington In connection with our February 2015 acquisition of Trulia, we assumed a lease agreement for office space in Bellevue for approximately 72,000 square feet of office space. In September 2015, in connection with our divestiture of Market Leader (see Note 8), Constellation assumed the Bellevue operating lease. Irvine, California In April 2012, we entered into a lease agreement for office space in Irvine (as amended from time to time, the “Irvine Lease”). Pursuant to the terms of the Irvine Lease, we lease a total of approximately 60,000 square feet under which we are obligated to make escalating monthly lease payments which began in August 2012 and continue through July 2022. We lease additional office space in San Francisco, California, Chicago, Illinois, Denver, Colorado, Cincinnati, Ohio, Lincoln, Nebraska and Vancouver, British Columbia. Future minimum payments for all operating leases as of December 31, 2015 are as follows (in thousands): 2016 $ 17,885 2017 21,702 2018 23,222 2019 21,909 2020 22,439 All future years 80,953 Total future minimum lease payments $ 188,110 Rent expense for the years ended December 31, 2015, 2014 and 2013, was $14.9 million, $7.5 million and $4.1 million, respectively. Total minimum rentals to be received in the future under noncancelable subleases as of December 31, 2015 was $4.3 million. Purchase Commitments As of December 31, 2015, we had non-cancelable purchase commitments for content related to our mobile applications and websites totaling $99.7 million. The amounts due for this content as of December 31, 2015 are as follows (in thousands): 2016 $ 34,330 2017 34,841 2018 14,000 2019 6,000 2020 6,000 2021 4,500 Total future purchase commitments $ 99,671 Letters of Credit As of December 31, 2015, we have outstanding letters of credit of approximately $4.6 million, $1.8 million, $1.5 million, $1.1 million and $1.1 million which secure our lease obligations in connection with the operating leases of our San Francisco, Seattle, Bellevue, New York and Denver office spaces, respectively. Certain of the letters of credit are unsecured obligations, and certain of the letters of credit are secured by certificates of deposit held as collateral in our name at a financial institution. The secured letters of credit are classified as restricted cash in our consolidated balance sheet. Surety Bonds In the course of business, we are required to provide financial commitments in the form of surety bonds to third parties as a guarantee of our performance on and our compliance with certain obligations. If we were to fail to perform or comply with these obligations, any draws upon surety bonds issued on our behalf would then trigger our payment obligation to the surety bond issuer. We have outstanding surety bonds issued for our benefit of approximately $3.4 million as of December 31, 2015. There were no surety bonds outstanding as of December 31, 2014. Legal Proceedings We are involved in a number of legal proceedings concerning matters arising in connection with the conduct of our business activities, some of which are at preliminary stages and some of which seek an indeterminate amount of damages. We regularly evaluate the status of legal proceedings in which we are involved to assess whether a loss is probable or there is a reasonable possibility that a loss or additional loss may have been incurred to determine if accruals are appropriate. We further evaluate each legal proceeding to assess whether an estimate of possible loss or range of loss can be made if accruals are not appropriate. For certain cases described below, management is unable to provide a meaningful estimate of the possible loss or range of possible loss because, among other reasons, (i) the proceedings are in preliminary stages; (ii) specific damages have not been sought; (iii) damages are, in our view, unsupported and/or exaggerated; (iv) there is uncertainty as to the outcome of pending appeals or motions; (v) there are significant factual issues to be resolved; and/or (vi) there are novel legal issues or unsettled legal theories presented. For these cases, however, management does not believe, based on currently available information, that the outcomes of these proceedings will have a material effect on our financial position, results of operations or cash flow. In March 2010, Smarter Agent, LLC (“Smarter Agent”) filed a complaint against us and multiple other defendants, including HotPads, Inc. (“HotPads”), for patent infringement in the U.S. District Court for the District of Delaware. The complaint alleges, among other things, that our mobile technology infringes three patents held by Smarter Agent purporting to cover: a “Global positioning-based real estate database access device and method,” a “Position-based information access device and method” and a “Position-based information access device and method of searching,” and seeks an injunction against the alleged infringing activities and an unspecified award for damages. In November 2010, the U.S. Patent and Trademark Office granted our petition for re-examination of the three patents-in-suit, and, to date, all claims of all three patents remain rejected in the re-examination proceedings, including through appeals to the Patent Trial and Appeal Board. In March 2011, the court granted a stay of the litigation pending the completion of the re-examination proceedings. In addition, in October 2011, Smarter Agent filed a substantially similar complaint against Diverse Solutions, Inc. (“Diverse Solutions”), StreetEasy, Market Leader (a subsidiary of Trulia), and other defendants, for patent infringement in the U.S. District Court for the District of Delaware. On October 31, 2011, we acquired substantially all of the operating assets and certain liabilities of Diverse Solutions, including the Smarter Agent complaint against Diverse Solutions. On December 14, 2012, we acquired HotPads, and took responsibility for the Smarter Agent complaint against HotPads. On August 26, 2013, we acquired StreetEasy, and took responsibility for the Smarter Agent complaint against StreetEasy. On February 17, 2015, we acquired Trulia, and took responsibility for the Smarter Agent complaint against Market Leader. On September 22, 2015, the court dismissed the case against Zillow, HotPads, and Trulia. On September 25, 2015, the court dismissed the case against Market Leader and Diverse Solutions. On October 6, 2015, the court dismissed the case against StreetEasy. We have not recorded an accrual related to these complaints as of December 31, 2015 or 2014, as the complaints have been dismissed. In September 2010, LendingTree, LLC (“LendingTree”) filed a complaint against us for patent infringement in the U.S. District Court for the Western District of North Carolina. The complaint alleged, among other things, that our website technology infringes two patents purporting to cover a “Method and computer network for coordinating a loan over the internet.” The complaint sought, among other things, a judgment that we infringed certain patents held by LendingTree, an injunction against the alleged infringing activities and an award for damages. We denied the allegations and asserted defenses and counterclaims seeking declarations that we are not infringing the patents and that the patents are invalid. In March 2014, a federal jury found that Zillow does not infringe the patents and that the patents asserted by LendingTree are invalid. In April, 2014, LendingTree filed two motions for judgment as a matter of law and for a new trial, all of which we opposed. In October 2014, the Court issued an order upholding the jury verdict and denying LendingTree’s motions. In November 2014, LendingTree filed a notice of appeal and, in September 2015, LendingTree filed its opening brief. In December 2015, we filed a response brief to LendingTree’s opening brief. We have not recorded an accrual related to this complaint as of December 31, 2015 or 2014, as we do not believe a loss is probable or reasonably estimable. In March 2014, Move, Inc., the National Association of Realtors and three related entities, filed a complaint against us and Errol Samuelson, our Chief Industry Development Officer, in the Superior Court of the State of Washington in King County, alleging, among other things, that Zillow and Mr. Samuelson misappropriated plaintiffs’ trade secrets in connection with Mr. Samuelson joining Zillow in March 2014. The plaintiffs seek, among other things, an injunction against the alleged misappropriations and Mr. Samuelson working for us, as well as significant monetary damages. In February 2015, plaintiffs filed an amended complaint that, among other things, added Curt Beardsley, our Vice President of MLS Partnerships, as a defendant in the matter. In August 2015, Zillow filed an amended answer and counterclaim against plaintiffs that alleged, among other things, that plaintiffs violated the Washington Trade Secrets Act and aided and abetted a breach of the duty of confidentiality through the public filing of a document that included Zillow’s confidential information and trade secrets. On January 8, 2016, plaintiffs filed a motion seeking sanctions against defendants for alleged evidence spoliation, and defendants each filed a motion for partial summary judgment against plaintiffs regarding the preemption of their common law claims by the Uniform Trade Secrets Act. A hearing was held on February 5, 2016 regarding the motions that the court is currently taking under advisement. An evidentiary hearing regarding plaintiffs’ spoliation motion has been scheduled for April 2016. The trial date is scheduled for June 2016. The plaintiffs recently indicated that they are seeking damages which, if actually awarded, would have a material adverse effect on our business. We believe the plaintiffs’ allegations are without merit and their calculations of damages are baseless. We deny the allegations of any wrongdoing and intend to vigorously defend the claims in the lawsuit. We have not recorded an accrual related to these complaints as of December 31, 2015 or 2014, as we do not believe a loss is probable. There is a reasonable possibility that a loss may be incurred; however, the possible loss or range of loss is not estimable. In August 2014, four purported class action lawsuits were filed by plaintiffs against Trulia and its directors, Zillow, and Zebra Holdco, Inc. in connection with Zillow’s proposed acquisition of Trulia. One of those purported class actions, captioned Collier et al. v. Trulia, Inc., et al., was brought in the Superior Court of the State of California for the County of San Francisco, however on October 7, 2014, plaintiff in the Collier action filed a new complaint in the Delaware Court of Chancery alleging substantially the same claims and seeking substantially the same relief as the original complaint filed in California. On October 8, 2014, plaintiff in the Collier action filed a request for dismissal of the California case without prejudice. The other three of the purported class action lawsuits, captioned Shue et al. v. Trulia, Inc., et al., Sciabacucci et al. v. Trulia, Inc., et al., and Steinberg et al. v. Trulia, Inc. et al., were brought in the Delaware Court of Chancery. All four lawsuits allege that Trulia’s directors breached their fiduciary duties to Trulia stockholders, and that the other defendants aided and abetted such breaches, by seeking to sell Trulia through an allegedly unfair process and for an unfair price and on unfair terms. All lawsuits sought, among other things, equitable relief that would have enjoined the consummation of Zillow’s proposed acquisition of Trulia and attorneys’ fees and costs. The Delaware actions also seek rescission of the Merger Agreement or rescissory damages and orders directing the defendants to account for alleged damages suffered by the plaintiffs and the purported class as a result of the defendants’ alleged wrongdoing. On September 24, 2014, plaintiff in the Sciabacucci action filed (1) a motion for expedited proceedings, (2) a motion for a preliminary injunction, (3) a request for production of documents from defendants, and (4) notice of depositions. On October 13, 2014, the Delaware Court of Chancery issued an order consolidating all of the Delaware actions into one matter captioned In re Trulia, Inc. Stockholder Litigation. On October 13 and 14, 2014, the above-referenced motions were refiled under the consolidated case number. On November 14, 2014, plaintiffs again refiled their motion for a preliminary injunction challenging the proposed acquisition. On November 19, 2014, the parties entered into a Memorandum of Understanding, documenting an agreement-in-principle for the settlement of the consolidated litigation, pursuant to which Trulia agreed to make certain supplemental disclosures in a Form 8-K. The Memorandum of Understanding was filed with the Court of Chancery that same day. Thereafter, the parties negotiated and agreed to a stipulation of settlement, and after notice to the class, the Court of Chancery held a settlement hearing on September 16, 2015 where the Court requested the parties to make further submission in connection with the settlement. By an opinion dated January 22, 2016, the Court denied approval of the settlement. We have not recorded an accrual related to these complaints as of December 31, 2015 or 2014, as we do not believe a loss is probable. In July 2015, two purported class action lawsuits were filed against us and each of our directors in the Superior Court of the State of Washington in King County, alleging, among other things, that the directors breached their fiduciary duties in connection with the approval of the issuance of non-voting Class C capital stock as a dividend. The complaints seek, among other things, injunctive relief and unspecified monetary damages. A hearing on the plaintiffs’ motion seeking a preliminary injunction to enjoin the issuance of the Class C Stock Split was held on August 5, 2015, and the court denied plaintiffs’ motion for a preliminary injunction. Plaintiffs filed a consolidated class action complaint on September 18, 2015 naming and seeking relief from only our co-founders as defendants. On December 4, 2015, defendents filed a motion to dismiss the consolidated class action complaint, and a hearing to consider that motion to dismiss is scheduled for March 2016. We have not recorded an accrual related to this purported class action lawsuit as of December 31, 2015, as we do not believe a loss is probable. In March 2015, the Wage and Hour Division of the U.S. Department of Labor (“DOL”) notified the Company that it was initiating a compliance review to determine the Company’s compliance with one or more federal labor laws enforced by the DOL. The Company understands that the scope of this review is limited to the review of the Company’s compliance with certain wage and hour laws with respect to Zillow, Inc. inside sales consultants during a two-year period between 2013 and 2015. In October 2015, the DOL orally informed us that the compliance review is ongoing but that, based on its preliminary findings, it believes the Company may have failed to pay overtime to such inside sales consultants. The DOL has made no assessment of damages or penalties, however, nor has it made a determination that we violated one or more federal labor laws. We have cooperated and continue to cooperate with the DOL in its compliance review. If the DOL were to finally determine that we violated one or more federal labor laws, we may be required to make certain payments of back wages and other amounts to such inside sales consultants or take other corrective actions, and may be subject to fines or penalties. We have recorded an accrual for an immaterial amount as of December 31, 2015 related to liabilities that may result from this compliance review. There is a reasonable possibility that a loss in excess of amounts accrued may be incurred; however, any additional possible loss or range of loss is not reasonably estimable at this time because the DOL’s review is ongoing, and we are unable to predict the outcome of the review. In addition to the matters discussed above, from time to time, we are involved in litigation and claims that arise in the ordinary course of business. Although we cannot be certain of the outcome of any litigation and claims, nor the amount of damages and exposure that we could incur, we currently believe that the final disposition of such matters will not have a material effect on our financial position, results of operations or cash flow. Regardless of the outcome, litigation can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors. Indemnifications In the ordinary course of business, we enter into contractual arrangements under which we agree to provide indemnification of varying scope and terms to business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of the breach of such agreements and out of intellectual property infringement claims made by third parties. In addition, we have agreements that indemnify certain issuers of surety bonds against losses that they may incur as a result of executing surety bonds on our behalf. For our indemnification arrangements, payment may be conditional on the other party making a claim pursuant to the procedures specified in the particular contract. Further, our obligations under these agreements may be limited in terms of time and/or amount, and in some instances, we may have recourse against third parties for certain payments. In addition, we have indemnification agreements with certain of our directors and executive officers that require us, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The terms of such obligations may vary.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2015
Restructuring and Related Activities [Abstract]
Restructuring	Note 18. Restructuring On February 17, 2015, in connection with the February 2015 acquisition of Trulia, Zillow Group undertook a restructuring plan that resulted in a total workforce reduction of nearly 350 employees, primarily to eliminate overlapping positions in the sales and marketing functions related to Trulia’s workforce at its Bellevue, Denver, New York and San Francisco locations. The restructuring plan is a result of the integration of Trulia’s business and operations with and into Zillow Group’s business. Employees directly affected by the restructuring plan were provided with severance payments, stock vesting acceleration and outplacement assistance. Primarily as a result of the restructuring plan, Zillow Group recorded a restructuring charge of approximately $35.6 million during the year ended December 31, 2015, including approximately $12.2 million for severance and other personnel related expenses, approximately $8.2 million for contract termination costs associated with certain operating leases, and approximately $14.9 million of non-cash expenses relating to stock vesting acceleration or a reduced remaining requisite service period, for which share-based compensation expense is recognized over the remaining requisite service period, which in some cases may result in immediate expense recognition if no substantive future service is required. Zillow Group recognized certain contract termination costs primarily associated with Trulia’s Bellevue operating lease, as well as Zillow’s San Francisco operating lease, as Zillow’s employees in San Francisco were relocated into Trulia’s San Francisco office space. The restructuring costs for contract termination costs for the year ended December 31, 2015 include approximately $4.0 million, primarily related to the write-off of certain leasehold improvements. In connection with our February 2015 acquisition of Trulia, we also assumed certain restructuring liabilities due to Trulia’s restructuring that commenced in June 2014 as an ongoing effort to fully integrate Market leader’s operations. The Market Leader restructuring resulted in a reduction of headcount of approximately 80 employees in 2014, as well as the recognition of certain contract termination costs associated with Trulia’s Bellevue and Denver operating leases. These restructuring liabilities were transferred in connection with the September 2015 divestiture of Market Leader. A summary of accrued restructuring costs as of and for the year ended December 31, 2015 is shown in the table below (in thousands): One-Time Termination Benefits Contract Termination Costs Other Associated Costs Total Restructuring liabilities assumed in connection with February 2015 acquisition of Trulia $ 81 $ 2,544 $ 136 $ 2,761 Restructuring costs 11,933 1,508 315 13,756 Cash payments (12,111 ) (1,557 ) (580 ) (14,248 ) Change in estimate 97 2,285 129 2,511 Restructuring liabilities transferred in connection with September 2015 divestiture of Market Leader — (4,611 ) — (4,611 ) Accrued restructuring costs as of December 31, 2015 $ — $ 169 $ — $ 169 As of December 31, 2015, the restructuring plan is substantially complete.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	Note 19. Related Party Transactions In February 2015, we paid approximately $0.3 million in filing fees directly to the Federal Trade Commission (the “FTC”), on behalf of and in connection with filings made by Mr. Richard Barton, our Executive Chairman, under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (“HSR Act”), which filings were required due to Mr. Barton’s ownership of Zillow, Inc.’s common stock. Also, in February 2015, we paid approximately $0.1 million in filing fees directly to the FTC, on behalf of and in connection with a filing made by Mr. Lloyd Frink, our Vice Chairman and President, under the HSR Act, which filing was required due to Mr. Frink’s ownership of Zillow, Inc.’s common stock. During the year ended December 31, 2015, we paid or have payable a total of approximately $0.2 million and $0.2 million, respectively, to Mr. Frink and Mr. Barton for reimbursement of costs incurred by Mr. Frink and Mr. Barton for use of private planes by certain of the Company’s employees and Mr. Frink and Mr. Barton for business travel.

Self-Insurance

Self-Insurance	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Self-Insurance	Note 20. Self-Insurance We are self-insured for a portion of our medical and dental coverage for certain employees of Trulia. The medical plan carries a stop-loss policy, which will protect from individual claims during the plan year exceeding $100,000 or when cumulative medical claims exceed 125% of expected claims for the plan year. We record estimates of the total costs of claims incurred based on an analysis of historical data and independent estimates. Our liability for self-insured medical and dental claims is included within accrued compensation and benefits in our consolidated balance sheet and was $0.5 million as of December 31, 2015. We did not have any self-insurance prior to our February 2015 acquisition of Trulia.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Postemployment Benefits [Abstract]
Employee Benefit Plan	Note 21. Employee Benefit Plan Effective January 1, 2015, Zillow Group established a defined contribution 401(k) retirement plan covering employees who have met certain eligibility requirements (“the Zillow Group 401(k) Plan”). In addition, in connection with our February 2015 acquisition of Trulia, we adopted a defined contribution 401(k) retirement plan that covers Trulia and Market Leader employees who have met certain eligibility requirements (“the Trulia 401(k) Plan”). Eligible employees under each of the plans may contribute pretax compensation up to a maximum amount allowable under the Internal Revenue Service limitations. Employee contributions and earnings thereon vest immediately. We currently match up to 1.5% of employee contributions under the Zillow Group 401(k) Plan and up to 4% of employee contributions under the Trulia 401(k) Plan. The total expense related to defined contribution 401(k) retirement plans was $4.2 million for the year ended December 31, 2015. We did not have any expense related to defined contribution 401(k) retirement plans for the years ended December 31, 2014 or 2013.

Segment Information and Revenue

Segment Information and Revenue	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information and Revenue	Note 22. Segment Information and Revenue We have one reportable segment. Our reportable segment has been identified based on how our chief operating decision-maker manages our business, makes operating decisions and evaluates operating performance. The chief executive officer acts as the chief operating decision-maker and reviews financial and operational information on an entity-wide basis. We have one business activity and there are no segment managers who are held accountable for operations, operating results or plans for levels or components. Accordingly, we have determined that we have a single reporting segment and operating unit structure. The chief executive officer reviews information about revenue categories, including marketplace revenue and display revenue. The following table presents our revenue categories during the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Marketplace revenue: Real estate $ 482,092 $ 239,039 $ 132,901 Mortgages 44,263 28,203 21,812 Market Leader 29,549 — — Total Marketplace revenue 555,904 267,242 154,713 Display revenue 88,773 58,651 42,832 Total revenue $ 644,677 $ 325,893 $ 197,545

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	Note 23. Subsequent Events On February 2, 2016, Zillow, Inc., Nectarine Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of Zillow, Inc. (“Merger Sub”), Naked Apartments, Inc., a Delaware corporation (“Naked Apartments”), and an individual acting as the stockholder representative, entered into an Agreement and Plan of Merger (the “Naked Apartments Merger Agreement”) providing for the acquisition of Naked Apartments by Zillow, Inc. Under the terms and subject to the conditions of the Naked Apartments Merger Agreement, Merger Sub will merge with and into Naked Apartments, with Naked Apartments remaining as the surviving company and a wholly owned subsidiary of Zillow, Inc. (the “Naked Apartments Merger”). Naked Apartments is New York City’s largest rentals-only platform. The purchase price will be approximately $13 million in cash, less certain transaction expenses and as adjusted at closing based on Naked Apartments’s net working capital, cash and debt. The acquisition of Naked Apartments, which is expected to close in the first quarter of 2016 subject to satisfaction of customary closing conditions, will be accounted for as a business combination, and assets acquired and liabilities assumed will be recorded at their estimated fair values as of the closing date of the Naked Apartments Merger.

Summary of Significant Accoun33

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include Zillow Group, Inc. and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. These consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”). For financial reporting and accounting purposes, Zillow was the acquirer of Trulia. The results presented in the consolidated financial statements and the notes to consolidated financial statements reflect those of Zillow prior to the completion of the acquisition of Trulia on February 17, 2015, and Trulia’s results of operations have been included prospectively after February 17, 2015. On August 14, 2015, Zillow Group completed a stock dividend in the form of two shares of Class C capital stock for each share of Class A common stock and Class B common stock outstanding as of July 31, 2015. The stock dividend had the effect of a 3-for-1 stock split. All references made to share or per share amounts in the accompanying consolidated financial statements and applicable disclosures have been retroactively adjusted to reflect the stock split. See Note 12, Note 14 and Note 15 for additional information about the stock split effected in the form of a stock dividend.
Use of Estimates	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 revenue recognition, website development costs, recoverability of long-lived assets and intangible assets with definite lives, share-based compensation, income taxes, business combinations, goodwill, and restructuring, among others. To the extent there are material differences between these estimates, judgments, or assumptions and actual results, our financial statements will be affected.
Reclassifications	Reclassifications Certain immaterial reclassifications have been made in the consolidated statements of operations and statements of cash flows to conform data for prior periods to the current format.
Concentrations of Credit Risk	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 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.
Restricted Cash	Restricted Cash Restricted cash consists of certificates of deposit held as collateral in our name at a financial institution related to certain of our operating leases.
Investments	Investments Our investments consist of fixed income securities, which include U.S. and foreign government agency securities, corporate notes and bonds, municipal securities, commercial paper and certificates of deposit, and are classified as available-for-sale securities beginning on January 1, 2015. 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 December 31, 2015 or December 31, 2014. Prior to January 1, 2015 our investments were classified as held-to-maturity and were recorded at amortized cost (see Note 4).
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts 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.
Property and Equipment	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 3 years Purchased software 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 differences between the proceeds received and the net book value of the disposed asset.
Website and Software Development Costs	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 year. 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.
Goodwill	Goodwill Goodwill represents the excess of the cost of an acquired business over the fair value of the assets acquired at the date of acquisition. 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. We assess goodwill for possible impairment by first performing a qualitative assessment to determine whether it is more likely than not that the fair value of our reporting unit is less than its carrying amount. If we determine that it is not more likely than not that the fair value of our reporting unit is less than its carrying amount, then the first and second steps of the goodwill impairment test are unnecessary. If we determine that it is more likely than not that the fair value of our reporting unit is less than its carrying amount, we perform the two-step goodwill impairment test. The first step of the goodwill impairment test identifies if there is potential goodwill impairment. If step one indicates that an impairment may exist, a second step is performed to measure the amount of the goodwill impairment, if any. Goodwill impairment exists when the estimated fair value of goodwill is less than its carrying value. If impairment exists, the carrying value of the goodwill is reduced to fair value through an impairment charge recorded in our statements of operations.
Intangible Assets	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 life of 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 amortize the total contract value over the estimated useful life. For contracts in which we have perpetual rights to the data, the total contract value is amortized on a straight-line basis over the life of the contract plus two years, which is equivalent to the estimated useful life of the asset. For contracts in which we do not have access to the data beyond the contractual term, the total contract value is amortized on a straight line basis over the term of the contract. 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 ranges from two to nine 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 websites and mobile applications. 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 have intangible assets for developed technology, customer relationships, trade names and trademarks, advertising relationships and MLS home data feeds 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 Deferred revenue consists of prepaid advertising fees received or billed in advance of the delivery or completion of the services, prepaid but unrecognized subscription revenue, and for amounts received in instances when revenue recognition criteria have not been met. Deferred revenue is recognized when the services are provided and all revenue recognition criteria have been met.
Deferred Rent	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.
Restructuring	Restructuring The main components of our restructuring plan related to the February 2015 acquisition of Trulia relate to workforce reduction and contract termination costs. Workforce reduction charges are accrued when it is probable that the employees are entitled to the severance payments and the amounts can be reasonably estimated. One-time involuntary termination benefits are accrued when the plan of termination has been communicated to the employees and certain other criteria are met. Share-based compensation expense related to acceleration of share-based awards assumed in connection with the acquisition of Trulia is recognized over the remaining requisite service period. Contract termination costs are recognized as a liability when a contract is terminated in accordance with its terms or at the cease-use date. The cumulative effect of a change resulting from a revision to either the timing or the amount of estimated cash flows is recognized as an adjustment to the liability in the period of the change. If the amounts and timing of cash flows from restructuring activities are significantly different from what we have estimated, the actual amount of restructuring and other related charges could be materially different than those we have recorded. Further details on the restructuring are presented in Note 18 of these consolidated financial statements.
Business Combinations	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 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. Further details on the February 2015 acquisition of Trulia and the August 2015 acquisition of DotLoop, Inc. are presented in Note 7 of these consolidated financial statements.
Revenue Recognition	Revenue Recognition In general, we recognize revenue when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered to the customer, (iii) the fee is fixed or determinable, and (iv) collectability is reasonably assured. We consider a signed agreement, a binding insertion order or other similar documentation reflecting the terms and conditions under which products or services will be provided to be persuasive evidence of an arrangement. Collectability is assessed based on a number of factors, including payment history and the creditworthiness of a customer. If it is determined that collection is not reasonably assured, revenue is not recognized until collection becomes reasonably assured, which is generally upon receipt of cash. We generate revenue from the sale of advertising services and our suite of tools to businesses and professionals primarily associated with the real estate and mortgage industries. These professionals include local real estate professionals, mortgage professionals and brand advertisers. Our two revenue categories are marketplace revenue and display revenue. Incremental direct costs incurred related to the acquisition or origination of a customer contract in a transaction that results in the deferral of revenue are expensed as incurred. Marketplace Revenue. Real estate revenue primarily includes revenue from advertising and a suite of tools sold to real estate professionals, as well as revenue generated by Zillow Group Rentals, which includes our rentals marketplace and suite of tools for rental professionals. In August 2015, Zillow Group completed the integration of certain Zillow and Trulia agent advertising products, effectively eliminating the Trulia Local Ads and Trulia Mobile Ads products. As a result of the integration, Agent Advertisers can manage their advertising across both Zillow and Trulia mobile and Web through the combined Premier Agent platform. Our Zillow Premier Agent program, which is included in real estate revenue, offers a suite of marketing and business technology solutions to help real estate agents grow their businesses and personal brands. The Premier Agent program allows agents to select products and services that they can tailor to meet their business and advertising needs. The program has three tiers of participation including Premier Platinum, our flagship product, as well as Premier Gold and Premier Silver, to meet different marketing and business needs of a broad range of agents. All tiers of Premier Agents receive access to a dashboard portal on our website that provides individualized program performance analytics, as well as our personalized website service, and our free customer relationship management, or CRM, tool that captures detailed information about each contact made with a Premier Agent through our mobile and web platforms. Our Premier Gold product also includes featured listings whereby the agent’s listings will appear at the top of search results on our mobile and web platforms. Our Premier Platinum product includes the dashboard portal on our website, our personalized website service, our CRM tool, featured listings, and inclusion on our buyer’s agent list, whereby the agent appears as the agent to contact for listings in the purchased zip code. We charge for our Platinum Premier Agent product based on the number of impressions delivered on our buyer’s agent list in zip codes purchased and a contracted maximum cost per impression. Our Platinum Premier Agent product includes multiple deliverables which are accounted for as a single unit of accounting, as the delivery or performance of the undelivered elements is based on traffic to our mobile applications and websites. We recognize revenue related to our impression-based Platinum Premier Agent product based on the lesser of (i) the actual number of impressions delivered on our buyer’s agent list during the period multiplied by the contracted maximum cost per impression, or (ii) the contractual maximum spend on a straight-line basis during the contractual period over which the services are delivered, typically over a period of six months or twelve months and then month-to-month thereafter. We charge a fixed subscription fee for Zillow’s Premier Gold and Premier Silver subscription products. Subscription advertising revenue for our Premier Gold and Premier Silver subscription products is recognized on a straight-line basis during the contractual period over which the services are delivered, typically over a period of six months and then month-to-month thereafter. Our Trulia real estate products included in real estate revenue are primarily sold on a fixed fee subscription basis, and include Trulia Local Ads, Trulia Mobile Ads, Trulia Pro with featured listings and Trulia Seller Ads. Prior to the August 2015 integration of certain of Zillow’s and Trulia’s advertising products, Trulia Local Ads and Trulia Mobile Ads enabled real estate professionals to promote themselves on Trulia’s search results pages and property details pages for a local market area. Real estate professionals purchased subscriptions to these products based upon their specified market share for a city or zip code, at a fixed monthly price, for periods ranging from one month to one year, with pricing depending on demand, location, and the percentage of market share purchased. Following the August 2015 agent advertising product integration, Trulia Local Ads and Trulia Mobile Ads products are no longer sold by Zillow Group. Trulia’s featured listings product allows real estate professionals to receive prominent placement of their listings in Trulia’s search results. Real estate professionals sign up for new subscriptions to this product at a fixed monthly price for periods that generally range from six months to 12 months. Trulia Seller Ads enable real estate professionals to generate leads from consumers interested in selling their homes. Subscription advertising revenue for Trulia’s real estate products included in real estate revenue is recognized on a straight-line basis during the contractual period over which the services are delivered. Rentals revenue, which is included in real estate revenue, primarily includes advertising sold to property managers and other rental professionals on a cost per lead and cost per lease generated basis. We recognize revenue as leads are delivered to rental professionals or as qualified leases are confirmed. Mortgages revenue primarily includes advertising sold to mortgage lenders and other mortgage professionals on a cost per lead basis, as well as 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 delivered. For our cost per lead mortgage advertising products, participating qualified mortgage professionals make a prepayment to gain access to consumers interested in connecting with mortgage professionals. Consumers who request rates for mortgage loans are presented with personalized quotes from participating mortgage professionals. We only charge mortgage professionals a fee when users contact mortgage professionals for more information regarding a mortgage loan quote. Mortgage professionals who exhaust their initial prepayment can then prepay additional funds to continue to participate in the marketplace. We recognize revenue when a user contacts a mortgage professional through Zillow Group’s mortgages platform. Market Leader revenue primarily includes revenue from the sale of a comprehensive premium software-as-a-service based marketing product typically sold to real estate professionals as a bundle of products under a fixed fee subscription. Market Leader revenue is included in our results of operations from February 17, 2015 through the date of divestiture of September 30, 2015 (see Note 8). Display Revenue. There were no customers that generated 10% or more of our total revenue in the years ended December 31, 2015, 2014 or 2013.
Cost of Revenue	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, costs to generate leads for customers, multiple listing services fees and costs associated with the operation of our data center and customer websites.
Technology and Development	Technology and Development Research and development costs are expensed as incurred and are recorded in technology and development expenses. These costs consist primarily of technology and development headcount related expenses including salaries, bonuses, benefits and share-based compensation expense primarily associated with developing new technologies. For the years ended December 31, 2015, 2014 and 2013, expenses attributable to research and development for our business totaled $163.8 million, $72.9 million and $41.7 million, respectively. Technology and development expenses also include amortization of intangible assets, including acquired intangible assets, purchased content and capitalized website development costs, and other data content expense.
Share-Based Compensation	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, including estimated forfeiture rates. 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 a combination of our historical volatility and the published historical volatilities of industry peers in the online publishing market representing the verticals in which we operate. Through June 30, 2015, we estimated the weighted-average expected life of the option awards as the average of the option vesting schedule and the term of the award, since we did not have sufficient historical exercise data to provide a reasonable basis upon which to estimate expected term due to the limited period of time share-based awards had been exercisable. Beginning July 1, 2015, we estimate the weighted-average expected life of the option awards based on our historical exercise data. Forfeiture rates are estimated using historical actual forfeiture trends as well as our judgment of future forfeitures. These rates are evaluated at least quarterly and any change in compensation expense is recognized in the period of the change. The estimation of option awards that will ultimately vest requires judgment, and to the extent actual results or updated estimates differ from our current estimates, such amounts will be recorded as a cumulative adjustment in the period the estimates are revised. We consider many factors when estimating expected forfeitures, including employee class and historical experience. Actual results, and future changes in estimates, may differ substantially from management’s current estimates. For issuances of restricted stock awards, 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 at the date of grant.
Advertising Costs	Advertising Costs Advertising costs are expensed as incurred. For the years ended December 31, 2015, 2014 and 2013, expenses attributable to advertising totaled $103.4 million, $73.1 million and $38.7 million, respectively. Advertising costs are recorded in sales and marketing expenses.
Income Taxes	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.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In November 2015, the Financial Accounting Standards Board (“FASB”) issued guidance on the balance sheet classification of deferred taxes. This standard requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. This guidance is effective for interim and annual reporting periods beginning after December 15, 2016, and early adoption is permitted. We adopted this guidance for the year ended December 31, 2015 on a retrospective basis. The adoption of this guidance has not had a material impact on our financial position, results of operations or cash flows, and did not have any effect on prior periods due to the full valuation allowance against our net deferred tax assets. In September 2015, the FASB issued guidance on simplifying the accounting for measurement-period adjustments in business combinations. This standard requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. This guidance is effective for interim and annual reporting periods beginning after December 15, 2015, and early adoption is permitted. We adopted this guidance for the year ended December 31, 2015. The adoption of this guidance has not had a material impact on our financial position, results of operations or cash flows. In April 2015, the FASB issued guidance related to a customer’s accounting for fees paid in a cloud computing arrangement. This standard provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. This guidance is effective for interim and annual reporting periods beginning after December 15, 2015, and early adoption is permitted. We adopted this guidance on January 1, 2016. The adoption of this guidance has not had a material impact on our financial position, results of operations or cash flows. In August 2014, the FASB issued guidance on the disclosure of uncertainties about an entity’s ability to continue as a going concern. This standard provides guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for annual reporting periods ending after December 15, 2016, and early adoption is permitted. We expect to adopt this guidance on January 1, 2017. We do not expect the adoption of this guidance to have any impact on our financial position, results of operations or cash flows. In May 2014, the FASB issued guidance on revenue recognition. This guidance provides that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance also requires more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The original effective date of this guidance was for interim and annual reporting periods beginning after December 15, 2016, early adoption is not permitted, and the guidance must be applied retrospectively or modified retrospectively. In July 2015, the FASB approved an optional one-year deferral of the effective date. As a result, we expect to adopt this guidance on January 1, 2018. We have not yet determined our approach to adoption or the impact the adoption of this guidance will have on our financial position, results of operations or cash flows, if any. In April 2014, the FASB issued guidance on reporting discontinued operations and disclosures of disposals of components of an entity. This standard raises the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. The guidance is effective for annual reporting periods ending after December 15, 2014. Early adoption is permitted but only for disposals that have not been reported in financial statements previously issued. We adopted this guidance on January 1, 2015. The adoption of this guidance has not had a material impact on our financial position, results of operations or cash flows.
Fair Value	Accounting standards define fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market in an orderly transaction between market participants on the measurement date. The standards also establish a fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. There are 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—Assets and liabilities valued based on observable market data for similar instruments, such as quoted prices for similar assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity; instruments valued based on the best available data, some of which is internally developed, and considers risk premiums that a market participant would require. We applied the following methods and assumptions in estimating our fair value measurements: Cash equivalents Investments Restricted cash
Net Loss Per Share	Basic net loss per share is computed by dividing net loss by the weighted-average number of shares (including Class A common stock, Class B common stock and Class C capital stock) outstanding during the period. In the calculation of basic net loss per share, undistributed earnings are allocated assuming all earnings during the period were distributed. Diluted net loss per share is computed by dividing net loss by the weighted-average number of shares (including Class A common stock, Class B common stock and Class C capital stock) outstanding during the period and potentially dilutive Class A common stock and Class C capital stock equivalents, except in cases where the effect of the Class A common stock or Class C capital stock equivalent would be antidilutive. Potential Class A common stock and Class C capital stock equivalents consist of Class A common stock and Class C capital stock issuable upon exercise of stock options and stock appreciation rights and Class A common stock and Class C capital stock underlying unvested restricted stock awards and unvested restricted stock units using the treasury stock method. Potential Class A common stock equivalents also include Class A common stock issuable upon conversion of the 2020 Notes using the if-converted method.
Segment Information and Revenue	We have one reportable segment. Our reportable segment has been identified based on how our chief operating decision-maker manages our business, makes operating decisions and evaluates operating performance. The chief executive officer acts as the chief operating decision-maker and reviews financial and operational information on an entity-wide basis. We have one business activity and there are no segment managers who are held accountable for operations, operating results or plans for levels or components. Accordingly, we have determined that we have a single reporting segment and operating unit structure.

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Useful Lives	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 3 years Purchased software 3 years Office equipment, furniture and fixtures 5 to 7 years Leasehold improvements Shorter of expected useful life or lease term

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Summary of Balances of Cash Equivalents and Investments	The following table presents the balances of assets measured at fair value on a recurring basis, by level within the fair value hierarchy, as of December 31, 2015 (in thousands): December 31, 2015 Total Level 1 Level 2 Cash equivalents: Money market funds $ 195,870 $ 195,870 $ — Certificates of deposit 1,622 — 1,622 Short-term investments: U.S. government agency securities 194,636 194,636 — Corporate notes and bonds 41,314 — 41,314 Municipal securities 39,853 — 39,853 Certificates of deposit 11,837 — 11,837 Foreign government securities 3,511 — 3,511 Restricted cash 3,015 — 3,015 Total $ 491,658 $ 390,506 $ 101,152 The following table presents the fair value, by level within the fair value hierarchy, of our cash equivalents and investments as of December 31, 2014 (in thousands): December 31, 2014 Total Level 1 Level 2 Cash equivalents: Money market funds $ 98,645 $ 98,645 $ — Foreign government securities 9,035 — 9,035 Certificates of deposit 2,975 — 2,975 Short-term investments: U.S. government agency securities 118,342 118,342 — Corporate notes and bonds 78,746 — 78,746 Municipal securities 26,256 — 26,256 Foreign government securities 8,570 — 8,570 Commercial paper 7,987 — 7,987 Certificates of deposit 6,928 — 6,928 Long-term investments: U.S. government agency securities 63,515 63,515 — Municipal securities 12,917 — 12,917 Corporate notes and bonds 6,694 — 6,694 Certificates of deposit 200 — 200 Total $ 440,810 $ 280,502 $ 160,308

Cash, Cash Equivalents, Inves36

Cash, Cash Equivalents, Investments and Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Market Value of Cash and Cash Equivalents, Available-for-Sale Investments and Restricted Cash	The following table presents the amortized cost, gross unrealized gains and losses, and estimated fair market value of our cash and cash equivalents, available-for-sale investments and restricted cash as of December 31, 2015 (in thousands): December 31, 2015 Amortized Gross Gross Estimated Cash $ 31,646 $ — $ — $ 31,646 Cash equivalents: Money market funds 195,870 — — 195,870 Certificates of deposit 1,622 — — 1,622 Short-term investments: U.S government agency securities 195,092 1 (457 ) 194,636 Corporate notes and bonds 41,390 1 (77 ) 41,314 Municipal securities 39,878 11 (36 ) 39,853 Certificates of deposit 11,839 1 (3 ) 11,837 Foreign government securities 3,516 — (5 ) 3,511 Restricted cash 3,015 — — 3,015 Total $ 523,868 $ 14 $ (578 ) $ 523,304
Available-for-Sale Investments by Contractual Maturity	The following table presents available-for-sale investments by contractual maturity date as of December 31, 2015 (in thousands): Amortized Cost Estimated Fair Market Value Due in one year or less $ 140,656 $ 140,551 Due after one year through two years 151,059 150,600 Total $ 291,715 $ 291,151

Accounts Receivable, Net (Table

Accounts Receivable, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Accounts Receivable	The following table presents the detail of accounts receivable as of the dates presented (in thousands): December 31, 2015 2014 Accounts receivable $ 30,740 $ 17,373 Unbilled accounts receivable 2,427 4,122 Less: allowance for doubtful accounts (3,378 ) (2,811 ) Accounts receivable, net $ 29,789 $ 18,684
Allowance for Doubtful Accounts	The following table presents the changes in the allowance for doubtful accounts for the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Allowance for doubtful accounts: Balance, beginning of period $ 2,811 $ 1,850 $ 965 Additions charged to expense 3,235 2,529 1,907 Less: write-offs, net of recoveries and other adjustments (2,668 ) (1,568 ) (1,022 ) Balance, end of period $ 3,378 $ 2,811 $ 1,850

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Detail of Property and Equipment	The following table presents the detail of property and equipment as of the dates presented (in thousands): December 31, 2015 2014 Website development costs $ 74,750 $ 65,224 Computer equipment 20,965 13,243 Leasehold improvements 32,918 10,617 Software 6,961 3,431 Construction-in-progress 15,630 9,307 Office equipment, furniture and fixtures 13,495 6,482 Property and equipment 164,719 108,304 Less: accumulated amortization and depreciation (75,080 ) (66,704 ) Property and equipment, net $ 89,639 $ 41,600

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Trulia
Summary of Purchase Price	The purchase price to effect the acquisition of Trulia of approximately $2.0 billion is summarized in the following table (in thousands): Value of Class A Common stock issued $ 1,883,728 Substituted stock options and stock appreciation rights attributable to pre-combination service 54,853 Substituted restricted stock units attributable to pre-combination service 27,798 Cash paid in lieu of fractional outstanding shares 41 Total purchase price $ 1,966,420
Purchase Price Allocation	Based upon the fair values determined by us, in which we considered or relied in part upon a valuation report of a third-party expert, the total purchase price was allocated as follows (in thousands): Cash and cash equivalents $ 173,447 Accounts receivable 13,093 Prepaid expenses and other current assets 20,833 Restricted cash 6,946 Property and equipment 30,189 Other assets 434 Identifiable intangible assets 549,000 Goodwill 1,736,362 Accounts payable, accrued expenses and other current liabilities (51,258 ) Accrued compensation and benefits (8,324 ) Deferred revenue (8,300 ) Long-term debt (230,000 ) Debt premium recorded in additional paid-in capital (126,386 ) Deferred tax liabilities and other long-term liabilities (139,616 ) Total preliminary estimated purchase price $ 1,966,420
Preliminary Estimated Fair Value of Identifiable Intangible Assets Acquired	The preliminary estimated fair value of identifiable intangible assets acquired consisted of the following (in thousands): Preliminary Fair Value Estimated Useful Life (in years) Trulia trade names and trademarks $ 351,000 Indefinite Market Leader trade names and trademarks 2,000 2 Customer relationships 92,000 3-7 Developed technology 91,000 3-7 Advertising relationships 9,000 3 MLS home data feeds 4,000 3 Total $ 549,000
Pro Forma Condensed Combined Financial Information	The following table presents the unaudited pro forma condensed combined financial information for the periods presented (in thousands): Year Ended December 31, 2015 (1) 2014 (2) Revenue $ 679,935 $ 577,830 Net loss $ (91,055 ) $ (83,336 ) (1) The year ended December 31, 2015 includes pro forma adjustments for $49.3 million to eliminate direct and incremental acquisition-related costs reflected in the historical financial statements, $37.3 million to eliminate share-based compensation expense attributable to substituted equity awards and to record additional share-based compensation expense attributable to substituted equity awards, $35.7 million to eliminate restructuring costs associated with the acquisition of Trulia reflected in the historical financial statements and $2.4 million to record additional amortization expense for acquired intangible assets. (2) The year ended December 31, 2014 includes pro forma adjustments for $39.5 million to eliminate direct and incremental acquisition-related costs reflected in the historical financial statements, $18.7 million to record additional amortization expense for acquired intangible assets, $10.7 million to eliminate share-based compensation expense attributable to substituted equity awards, $6.2 million to eliminate Trulia’s historical amortization of capitalized website development costs and $2.7 million to record additional rent expense.
DotLoop Inc
Summary of Purchase Price	The purchase price to effect the acquisition of DotLoop of approximately $105.5 million is summarized in the following table (in thousands): Cash paid for the outstanding stock and warrants of DotLoop $ 94,957 Cash paid for the cancellation of vested options to purchase shares of DotLoop’s common stock 5,640 Certain transaction expenses and other costs incurred by DotLoop 4,750 Substituted stock options attributable to pre-combination service 191 Total purchase price $ 105,538
Purchase Price Allocation	Based upon the fair values determined by us, in which we considered or relied in part upon a valuation report of a third-party expert, the total purchase price was allocated as follows (in thousands): Cash, cash equivalents, accounts receivable, prepaid expenses and other current assets $ 2,149 Property and equipment and other assets 258 Identifiable intangible assets 22,500 Goodwill 86,128 Accounts payable, accrued expenses and other current liabilities, accrued compensation and benefits, and deferred revenue (1,362 ) Deferred tax liabilities (4,135 ) Total preliminary estimated purchase price $ 105,538
Preliminary Estimated Fair Value of Identifiable Intangible Assets Acquired	The preliminary estimated fair value of identifiable intangible assets acquired consisted of the following (in thousands): Preliminary Fair Value Estimated Useful Life (in years) Developed technology $ 10,700 3 Customer relationships 10,200 6-7 Trade names and trademarks 1,600 3 Total $ 22,500

Divestiture of Market Leader (T

Divestiture of Market Leader (Tables)	12 Months Ended
	Dec. 31, 2015
Market Leader, Inc.
Schedule of Aggregate Carrying Amounts of Major Classes of Assets and Liabilities	The following table presents the aggregate carrying amounts of the major classes of assets and liabilities related to the Market Leader disposal group as of the date of divestiture of September 30, 2015 (in thousands): Assets Prepaid expenses and other current assets $ 501 Property and equipment, net 5,764 Goodwill 9,209 Intangible assets, net 17,161 Total assets $ 32,635 Liabilities Current liabilities $ 2,278 Other long-term liabilities 3,771 Total liabilities $ 6,049

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Change in Goodwill	The following table presents the change in goodwill from December 31, 2014 through December 31, 2015 (in thousands): Balance as of December 31, 2014 $ 96,352 Goodwill recorded in connection with the acquisition of Trulia 1,736,362 Goodwill recorded in connection with the acquisition of DotLoop 86,128 Reduction of goodwill in connection with the divestitures of businesses (9,675 ) Balance as of December 31, 2015 $ 1,909,167

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	The following tables present the detail of intangible assets subject to amortization as of the dates presented (in thousands): December 31, 2015 Cost Accumulated Net Purchased content $ 37,581 $ (19,649 ) $ 17,932 Customer relationships 103,425 (16,204 ) 87,221 Developed technology 108,295 (19,515 ) 88,780 Trade names and trademarks 4,860 (2,212 ) 2,648 Advertising relationships 9,000 (2,598 ) 6,402 MLS home data feeds 1,100 (318 ) 782 Total $ 264,261 $ (60,496 ) $ 203,765 December 31, 2014 Cost Accumulated Net Purchased content $ 24,615 $ (13,904 ) $ 10,711 Developed technology 13,595 (5,321 ) 8,274 Customer relationships 9,225 (3,387 ) 5,838 Trademarks 3,261 (1,327 ) 1,934 Total $ 50,696 $ (23,939 ) $ 26,757
Estimated Future Amortization Expense for Intangible Assets	Estimated future amortization expense for intangible assets, including amortization related to future commitments (see Note 17), as of December 31, 2015 is as follows (in thousands): 2016 $ 46,377 2017 44,090 2018 37,727 2019 32,906 2020 32,415 All future years 43,894 Total future amortization expense $ 237,409

Accrued Expenses and Other Cu43

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Summary of accrued expenses and other current liabilities	The following table presents the detail of accrued expenses and other current liabilities as of as of the dates presented (in thousands): December 31, 2015 2014 Accrued marketing and advertising $ 9,663 $ 1,509 Accrued purchased content 8,385 — Accrued legal fees 7,784 3,755 Merger consideration payable to former stockholders of StreetEasy, Inc. 5,317 5,317 Other accrued expenses and other current liabilities 11,898 6,302 Total accrued expenses and other current liabilities $ 43,047 $ 16,883

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components of Income Tax Benefit	The following table summarizes the components of our income tax benefit for the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Federal $ 2,838 $ — $ 3,783 State 1,807 — 328 Deferred income tax benefit $ 4,645 $ — $ 4,111
Reconciliation of Federal Statutory Rate and Effective Tax Rate	The following table presents a reconciliation of the federal statutory rate and our effective tax rate for the periods presented: Year Ended December 31, 2015 2014 2013 Tax expense at federal statutory rate (35.0 )% (34.0 )% (34.0 )% State income taxes, net of federal tax benefit (2.3 )% (1.5 )% (5.8 )% Nondeductible expenses 2.8 % 15.3 % 3.1 % Share-based compensation 1.2 % 0.7 % 0.2 % Research and development credits (4.1 )% (3.2 )% (23.3 )% Divestiture of businesses 2.3 % — — Other (1.0 )% — — Valuation allowance 33.1 % 22.7 % 35.0 % Effective tax rate (3.0 )% 0.0 % (24.8 )%
Deferred Tax Assets and Liabilities	The following table presents the significant components of our deferred tax assets and liabilities as of the dates presented (in thousands): December 31, 2015 2014 Deferred tax assets: Federal and state net operating loss carryforwards $ 162,521 $ 25,665 Share-based compensation 45,969 12,680 Goodwill 825 1,355 Depreciation and amortization 3,090 — Start-up and organizational costs 369 430 Research and development credits 21,157 6,493 Other tax credits 1,358 — Accruals and reserves 3,338 2,339 Deferred rent 5,228 4,248 Other deferred tax assets 550 167 Total deferred tax assets 244,405 53,377 Deferred tax liabilities: Website and software development costs (13,851 ) (7,263 ) Intangibles (200,082 ) (6,052 ) Other deferred tax liabilities (52 ) — Depreciation and amortization — (2,838 ) Net deferred tax assets before valuation allowance 30,420 37,224 Less: valuation allowance (162,715 ) (37,224 ) Net deferred tax assets (liabilities) $ (132,295 ) $ —
Changes in Unrecognized Tax Benefits	Changes for unrecognized tax benefits for the periods presented are as follows (in thousands): Balance at January 1, 2013 $ 1,255 Gross increases—prior and current period tax positions 3,868 Balance at December 31, 2013 $ 5,123 Gross increases—current period tax positions 1,946 Gross decreases—prior period tax positions (576 ) Balance at December 31, 2014 $ 6,493 Gross increases—prior and current period tax positions 3,577 Gross increases—assumed in connection with February 2015 acquisition of Trulia 3,910 Balance at December 31, 2015 $ 13,980

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Common and Capital Stock Reserved for Future Issuance	The following shares of common and capital stock have been reserved for future issuance as of the dates presented, and share numbers as of December 31, 2014 have been retroactively adjusted to reflect the effects of the Class C Stock Split defined below: December 31, December 31, Option awards outstanding 27,126,374 17,399,292 Restricted stock units outstanding 2,605,514 376,806 Class A common stock and Class C capital stock available for grant under 2011 Plan 688,014 2,017,818 Shares issuable upon conversion of outstanding Class B common stock 6,217,447 6,217,447 Total 36,637,349 26,011,363

Share-Based Awards (Tables)

Share-Based Awards (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Option Award and Stock Appreciation Rights Activity	The following table summarizes option award and stock appreciation rights activity for the year ended December 31, 2015 and has been retroactively adjusted to reflect the effects of the Class C Stock Split: Number Weighted- Weighted- Aggregate (in thousands) Outstanding at January 1, 2015 17,399,292 $ 18.12 5.32 $ 311,040 Assumed Trulia options and stock appreciation rights in connection with February 2015 acquisition of Trulia 3,159,765 13.79 Granted 11,438,095 31.45 Exercised (2,732,767 ) 8.99 Forfeited or cancelled (2,138,011 ) 28.37 Outstanding at December 31, 2015 27,126,374 23.35 5.96 156,025 Vested and exercisable at December 31, 2015 9,470,685 14.44 3.93 112,923
Fair Value of Options Granted, Excluding Stock Option Grant Program of Nonemployee Directors and Executives, Estimated at Date of Grant Using Black Scholes Merton Option Pricing Model	The fair value of options granted, excluding options granted under the Stock Option Grant Program for Nonemployee Directors (“Nonemployee Director Awards”) and certain options granted to the Company’s executives in January and February 2015 and January 2013, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model with the following assumptions for the periods presented: Year Ended December 31, 2015 2014 2013 Expected volatility 54% – 56% 53% – 57% 50% – 54% Expected dividend yield — — — Risk-free interest rate 1.03% – 1.48% 1.37% – 1.55% 0.70% – 1.27% Weighted-average expected life 3.50 – 4.58 years 4.58 years 4.58 years Weighted-average fair value of options granted $13.77 $14.78 $7.09
Summary of Restricted Stock Award Activity	The following table summarizes restricted stock award activity for the year ended December 31, 2015 and has been retroactively adjusted to reflect the effects of the Class C Stock Split: Shares of Weighted- Unvested outstanding at January 1, 2015 260,505 $ 10.75 Granted 4,173 40.45 Vested (233,732 ) 11.07 Forfeited or cancelled — — Unvested outstanding at December 31, 2015 30,946 12.35
Summary of Restricted Stock Units Activity	The following table summarizes activity for restricted stock units for the year ended December 31, 2015 and has been retroactively adjusted to reflect the effects of the Class C Stock Split: Restricted Stock Units Weighted- Unvested outstanding at January 1, 2015 376,806 $ 28.56 Assumed Trulia restricted stock units in connection with February 2015 acquisition of Trulia 3,798,957 36.38 Granted 1,354,185 28.55 Vested (1,899,531 ) 31.74 Forfeited or cancelled (1,024,903 ) 31.12 Unvested outstanding at December 31, 2015 2,605,514 32.36
Effects of Share Based Compensation in Consolidated Statements of Operations	The following table presents the effects of share-based compensation in our consolidated statements of operations during the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Cost of revenue $ 4,694 $ 1,844 $ 737 Sales and marketing 25,391 7,320 10,969 Technology and development 26,849 11,681 4,660 General and administrative 48,280 13,240 7,070 Restructuring costs 14,859 — — $ 120,073 $ 34,085 $ 23,436

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share	For the periods presented, the following Class A common stock and Class C capital stock equivalents were excluded from the calculations of diluted net loss per share because their effect would have been antidilutive, which share numbers have been retroactively adjusted to reflect the effects of the Class C Stock Split (in thousands): Year Ended December 31, 2015 2014 2013 Class A common stock and Class C capital stock issuable upon the exercise of option awards and stock appreciation rights 6,751 8,709 9,537 Class A common stock and Class C capital stock underlying unvested restricted stock awards and restricted stock units 639 354 513 Class A common stock issuable upon conversion of the 2020 Notes 9,535 — — Total Class A common stock and Class C capital stock equivalents 16,925 9,063 10,050

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Payments for All Operating Leases	Future minimum payments for all operating leases as of December 31, 2015 are as follows (in thousands): 2016 $ 17,885 2017 21,702 2018 23,222 2019 21,909 2020 22,439 All future years 80,953 Total future minimum lease payments $ 188,110
Purchase Commitments for Content Related to Mobile Applications and Websites	The amounts due for this content as of December 31, 2015 are as follows (in thousands): 2016 $ 34,330 2017 34,841 2018 14,000 2019 6,000 2020 6,000 2021 4,500 Total future purchase commitments $ 99,671

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2015
Restructuring and Related Activities [Abstract]
Summary of Accrued Restructuring Costs	A summary of accrued restructuring costs as of and for the year ended December 31, 2015 is shown in the table below (in thousands): One-Time Termination Benefits Contract Termination Costs Other Associated Costs Total Restructuring liabilities assumed in connection with February 2015 acquisition of Trulia $ 81 $ 2,544 $ 136 $ 2,761 Restructuring costs 11,933 1,508 315 13,756 Cash payments (12,111 ) (1,557 ) (580 ) (14,248 ) Change in estimate 97 2,285 129 2,511 Restructuring liabilities transferred in connection with September 2015 divestiture of Market Leader — (4,611 ) — (4,611 ) Accrued restructuring costs as of December 31, 2015 $ — $ 169 $ — $ 169

Segment Information and Reven50

Segment Information and Revenue (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Revenue Categories	The chief executive officer reviews information about revenue categories, including marketplace revenue and display revenue. The following table presents our revenue categories during the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Marketplace revenue: Real estate $ 482,092 $ 239,039 $ 132,901 Mortgages 44,263 28,203 21,812 Market Leader 29,549 — — Total Marketplace revenue 555,904 267,242 154,713 Display revenue 88,773 58,651 42,832 Total revenue $ 644,677 $ 325,893 $ 197,545

Organization and Description 51

Organization and Description of Business - Additional Information (Detail) $ in Thousands	Feb. 17, 2015USD ($)Employee	Jul. 28, 2014shares	Dec. 31, 2015USD ($)
Organization And Description Of Business [Line Items]
Business acquisition, effective date			Feb. 17, 2015
Agreement date			Jul. 28, 2014
Common stock exchange ratio	0.444
Total purchase price | $			$ 2,000,000
Trulia
Organization And Description Of Business [Line Items]
Business acquisition, effective date			Feb. 17, 2015
Total purchase price | $	$ 1,966,420
Total workforce reduction | Employee	350
Trulia | Class A Common Stock
Organization And Description Of Business [Line Items]
Common stock exchange ratio		0.444
Zillow Merger | Class A Common Stock
Organization And Description Of Business [Line Items]
Convertible common stock | shares		1
Zillow Merger | Class B Common Stock
Organization And Description Of Business [Line Items]
Convertible common stock | shares		1

Summary of Significant Accoun52

Summary of Significant Accounting Policies - Additional Information (Detail)	Aug. 14, 2015shares	Dec. 31, 2015USD ($)CategoriesCustomershares	Dec. 31, 2014USD ($)Customer	Dec. 31, 2013USD ($)Customer
Schedule Of Significant Accounting Policies [Line Items]
Business acquisition, effective date		Feb. 17, 2015
Stock split description		Outstanding equity awards to purchase or acquire shares of Class A common stock were proportionately adjusted to relate to one share of Class A common stock and two shares of Class C capital stock for each share of Class A common stock subject to the awards as of the record date, and the exercise prices of any such awards were also proportionately allocated between Class A common stock and Class C capital stock.
Stock split ratio	3
Other than temporary impairment loss		$ 0	$ 0
Amortization period, spread on perpetual rights contracts		2 years
Number of revenue categories | Categories		2
Sale of product for fixed subscription, description		Trulia real estate products included in real estate revenue are primarily sold on a fixed fee subscription basis, and include Trulia Local Ads, Trulia Mobile Ads, Trulia Pro with featured listings and Trulia Seller Ads. Prior to the August 2015 integration of certain of Zillow’s and Trulia’s advertising products, Trulia Local Ads and Trulia Mobile Ads enabled real estate professionals to promote themselves on Trulia’s search results pages and property details pages for a local market area. Real estate professionals purchased subscriptions to these products based upon their specified market share for a city or zip code, at a fixed monthly price, for periods ranging from one month to one year, with pricing depending on demand, location, and the percentage of market share purchased. Following the August 2015 agent advertising product integration, Trulia Local Ads and Trulia Mobile Ads products are no longer sold by Zillow Group. Trulia’s featured listings product allows real estate professionals to receive prominent placement of their listings in Trulia’s search results. Real estate professionals sign up for new subscriptions to this product at a fixed monthly price for periods that generally range from six months to 12 months. Trulia Seller Ads enable real estate professionals to generate leads from consumers interested in selling their homes.
Number of customers generating more than 10% of total revenue | Customer		0	0	0
Research and development expenses		$ 198,565,000	$ 84,669,000	$ 48,498,000
Advertising expenses		$ 103,400,000	$ 73,100,000	$ 38,700,000
Trulia
Schedule Of Significant Accounting Policies [Line Items]
Business acquisition, effective date		Feb. 17, 2015
Minimum | Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Schedule Of Significant Accounting Policies [Line Items]
Percentage of revenue		10.00%	10.00%	10.00%
First Set Of Product [Member]
Schedule Of Significant Accounting Policies [Line Items]
Purchase subscriptions to the products, maximum period		1 year
Purchase subscriptions to the products, minimum period		1 month
Second Set of Product
Schedule Of Significant Accounting Policies [Line Items]
Purchase subscriptions to the products, maximum period		12 months
Purchase subscriptions to the products, minimum period		6 months
Class C Capital Stock
Schedule Of Significant Accounting Policies [Line Items]
Dividend paid in shares for each class of common stock held as of record date | shares	2	2
Stock split description		On August 14, 2015, Zillow Group completed a stock dividend in the form of two shares of Class C capital stock for each share of Class A common stock and Class B common stock outstanding as of July 31, 2015. The stock dividend had the effect of a 3-for-1 stock split.
Technology and Development
Schedule Of Significant Accounting Policies [Line Items]
Research and development expenses		$ 163,800,000	$ 72,900,000	$ 41,700,000
Software Development
Schedule Of Significant Accounting Policies [Line Items]
Amortization period		1 year
Purchased Content | Minimum
Schedule Of Significant Accounting Policies [Line Items]
Amortization period		2 years
Purchased Content | Maximum
Schedule Of Significant Accounting Policies [Line Items]
Amortization period		9 years

Useful Lives (Detail)

Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2015
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	3 years
Purchased software
Property, Plant and Equipment [Line Items]
Property and equipment	3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	Shorter of expected useful life or lease term
Minimum | Office equipment, furniture, and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	5 years
Maximum | Office equipment, furniture, and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	7 years

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Original maturities date of money market funds	Less than three months
Liabilities measured at fair value	$ 0	$ 0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 0	$ 0

Fair Value of Cash Equivalents

Fair Value of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash	$ 3,015
Short-term investments	523,304
Total	491,658	$ 440,810
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	195,870	98,645
Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,622	2,975
Short-term investments	11,837
Short-term investments		6,928
Long-term investments		200
US Government Agencies Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	194,636
Short-term investments		118,342
Long-term investments		63,515
Corporate Notes and Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	41,314
Short-term investments		78,746
Long-term investments		6,694
Municipal Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	39,853
Short-term investments		26,256
Long-term investments		12,917
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		7,987
Foreign Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		9,035
Short-term investments	3,511
Short-term investments		8,570
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	390,506	280,502
Fair Value, Inputs, Level 1 | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	195,870	98,645
Fair Value, Inputs, Level 1 | US Government Agencies Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	194,636
Short-term investments		118,342
Long-term investments		63,515
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash	3,015
Total	101,152	160,308
Fair Value, Inputs, Level 2 | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,622	2,975
Short-term investments	11,837
Short-term investments		6,928
Long-term investments		200
Fair Value, Inputs, Level 2 | Corporate Notes and Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	41,314
Short-term investments		78,746
Long-term investments		6,694
Fair Value, Inputs, Level 2 | Municipal Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	39,853
Short-term investments		26,256
Long-term investments		12,917
Fair Value, Inputs, Level 2 | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		7,987
Fair Value, Inputs, Level 2 | Foreign Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		9,035
Short-term investments	$ 3,511
Short-term investments		$ 8,570

Cash, Cash Equivalents, Inves56

Cash, Cash Equivalents, Investments and Restricted Cash - Additional Information (Detail) $ in Millions	Jan. 01, 2015USD ($)
Cash and Cash Equivalents [Abstract]
Held to maturity transferred to available-for-sale security, unrealized loss	$ 0.1
Amount transferred from held-to-maturity to available-for-sale	$ 440.8

Amortized Cost, Gross Unrealize

Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Market Value of Cash and Cash Equivalents, Available-for-Sale Investments and Restricted Cash (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Cash and Cash Equivalents [Line Items]
Amortized Cost	$ 523,868
Gross Unrealized Gains	14
Gross Unrealized Losses	(578)
Estimated Fair Market Value	523,304
Cash
Cash and Cash Equivalents [Line Items]
Amortized Cost	31,646
Estimated Fair Market Value	31,646
Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Estimated Fair Market Value	11,837
US Government Agencies Debt Securities
Cash and Cash Equivalents [Line Items]
Estimated Fair Market Value	194,636
Corporate Notes and Bonds
Cash and Cash Equivalents [Line Items]
Estimated Fair Market Value	41,314
Municipal Securities
Cash and Cash Equivalents [Line Items]
Estimated Fair Market Value	39,853
Foreign Government Securities
Cash and Cash Equivalents [Line Items]
Estimated Fair Market Value	3,511
Restricted Cash
Cash and Cash Equivalents [Line Items]
Amortized Cost	3,015
Estimated Fair Market Value	3,015
Cash Equivalents | Money Market Funds
Cash and Cash Equivalents [Line Items]
Amortized Cost	195,870
Estimated Fair Market Value	195,870
Cash Equivalents | Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Amortized Cost	1,622
Estimated Fair Market Value	1,622
Short-term Investments | Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Amortized Cost	11,839
Gross Unrealized Gains	1
Gross Unrealized Losses	(3)
Estimated Fair Market Value	11,837
Short-term Investments | US Government Agencies Debt Securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	195,092
Gross Unrealized Gains	1
Gross Unrealized Losses	(457)
Estimated Fair Market Value	194,636
Short-term Investments | Corporate Notes and Bonds
Cash and Cash Equivalents [Line Items]
Amortized Cost	41,390
Gross Unrealized Gains	1
Gross Unrealized Losses	(77)
Estimated Fair Market Value	41,314
Short-term Investments | Municipal Securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	39,878
Gross Unrealized Gains	11
Gross Unrealized Losses	(36)
Estimated Fair Market Value	39,853
Short-term Investments | Foreign Government Securities
Cash and Cash Equivalents [Line Items]
Amortized Cost	3,516
Gross Unrealized Losses	(5)
Estimated Fair Market Value	$ 3,511

Available-for-Sale Investments

Available-for-Sale Investments by Contractual Maturity (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Cash and Cash Equivalents [Abstract]
Amortized Cost, Due in one year or less	$ 140,656
Amortized Cost, Due after one year through two years	151,059
Total	291,715
Estimated Fair Market Value, Due in one year or less	140,551
Estimated Fair Market Value, Due after one year through two years	150,600
Total	$ 291,151

Accounts Receivable (Detail)

Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Accounts receivable	$ 30,740	$ 17,373
Unbilled accounts receivable	2,427	4,122
Less: allowance for doubtful accounts	(3,378)	(2,811)	$ (1,850)	$ (965)
Accounts receivable, net	$ 29,789	$ 18,684

Allowance for Doubtful Accounts

Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts:
Balance, beginning of period	$ 2,811	$ 1,850	$ 965
Additions charged to expense	3,235	2,529	1,907
Less: write-offs, net of recoveries and other adjustments	(2,668)	(1,568)	(1,022)
Balance, end of period	$ 3,378	$ 2,811	$ 1,850

Detail of Property and Equipmen

Detail of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment	$ 164,719	$ 108,304
Less: accumulated amortization and depreciation	(75,080)	(66,704)
Property and equipment, net	89,639	41,600
Website development costs
Property, Plant and Equipment [Line Items]
Property and equipment	74,750	65,224
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	20,965	13,243
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	32,918	10,617
Software
Property, Plant and Equipment [Line Items]
Property and equipment	6,961	3,431
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property and equipment	15,630	9,307
Office equipment, furniture, and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	$ 13,495	$ 6,482

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Amortization and depreciation expense related to property and equipment other than website development costs	$ 12,200	$ 6,100	$ 3,500
Capitalization of website development costs	46,100	22,200	17,300
Amortization of website development costs and intangible assets included in technology and development	63,189	29,487	19,791
Technology and Development
Property, Plant and Equipment [Line Items]
Amortization of website development costs and intangible assets included in technology and development	39,300	11,100	7,600
Technology and Development | Software Development
Property, Plant and Equipment [Line Items]
Amortization of website development costs and intangible assets included in technology and development	$ 23,900	$ 18,300	$ 12,200

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail)	Aug. 20, 2015USD ($)	Feb. 17, 2015USD ($)$ / sharesshares	Jul. 28, 2014	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Business Acquisition [Line Items]
Acquisition-related costs				$ 16,576,000	$ 21,493,000	$ 376,000
Converted share of fully paid				At the effective time of the Trulia Merger, each share of Trulia common stock, other than Trulia excluded shares (as defined below), was converted into the right to receive 0.444 of a share of fully paid and nonassessable Zillow Group Class A common stock.
Common stock exchange ratio		0.444
Business acquisition, purchase price				$ 2,000,000,000
Closing price of stock on date of acquisition | $ / shares		$ 109.14
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, dividends				0.00%	0.00%	0.00%
Business acquisition, effective date				Feb. 17, 2015
Direct and incremental acquisition-related costs
Business Acquisition [Line Items]
Pro forma adjustments				$ 49,300,000	$ 39,500,000
Share-based compensation expense attributable to substituted equity awards
Business Acquisition [Line Items]
Pro forma adjustments				37,300,000	10,700,000
Restructuring costs associated with acquisition
Business Acquisition [Line Items]
Pro forma adjustments				35,700,000
Amortization expense of acquired intangible assets
Business Acquisition [Line Items]
Pro forma adjustments				2,400,000	18,700,000
Amortization of capitalized website development costs
Business Acquisition [Line Items]
Pro forma adjustments					6,200,000
Rent expense
Business Acquisition [Line Items]
Pro forma adjustments					$ 2,700,000
2.75% Convertible Senior Notes Due 2020
Business Acquisition [Line Items]
Preliminary fair value of Notes		$ 356,400,000		356,400,000
Debt instrument, aggregate principal amount		230,000,000		230,000,000
Debt premium recorded in additional paid-in capital				$ 126,400,000
2.75% Convertible Senior Notes Due 2020 | Class A Common Stock
Business Acquisition [Line Items]
Common stock exchange ratio				0.444
Trulia
Business Acquisition [Line Items]
Acquisition-related costs				$ 16,600,000
Business acquisition, purchase price		$ 1,966,420,000
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, expected volatility		53.00%
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, dividends		0.00%
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, risk-free interest rate		1.10%
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, expected life		3 years
Indefinite-lived intangible asset		$ 549,000,000
Deferred tax liability				$ 139,500,000
Business acquisition, effective date				Feb. 17, 2015
Trulia | Class A Common Stock
Business Acquisition [Line Items]
Common stock exchange ratio			0.444
Stock issued for acquisition | shares		17,259,704
Trulia | Trade Names and Trademarks
Business Acquisition [Line Items]
Indefinite-lived intangible asset		$ 351,000,000		$ 351,000,000
DotLoop Inc
Business Acquisition [Line Items]
Business acquisition, purchase price	$ 105,538,000
Indefinite-lived intangible asset	22,500,000
Deferred tax liability	$ 4,135,000
Business acquisition, effective date				Aug. 20, 2015
DotLoop Inc | Option Awards
Business Acquisition [Line Items]
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, expected volatility	55.00%
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, dividends	0.00%
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, risk-free interest rate	1.25%
Stock option and stock appreciation rights assumed of grant using the Black-Scholes-Merton option-pricing model, expected life	4 years 3 months 11 days

Summary of Purchase Price (Deta

Summary of Purchase Price (Detail) - USD ($) $ in Thousands	Aug. 20, 2015	Feb. 17, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Total purchase price			$ 2,000,000
Trulia
Business Acquisition [Line Items]
Cash paid in lieu of fractional outstanding shares		$ 41
Total purchase price		1,966,420
Trulia | Class A Common Stock
Business Acquisition [Line Items]
Value of stock issued and substituted share awards attributable to pre-combination service		1,883,728
Trulia | Stock Option and Stock Appreciation Rights
Business Acquisition [Line Items]
Value of stock issued and substituted share awards attributable to pre-combination service		54,853
Trulia | Restricted Stock Units
Business Acquisition [Line Items]
Value of stock issued and substituted share awards attributable to pre-combination service		$ 27,798
DotLoop Inc
Business Acquisition [Line Items]
Total purchase price	$ 105,538
Cash paid for the outstanding stock and warrants of DotLoop	94,957
Cash paid for the cancellation of vested options to purchase shares of DotLoop's common stock	5,640
Certain transaction expenses and other costs incurred by DotLoop	4,750
DotLoop Inc | Option Awards
Business Acquisition [Line Items]
Value of stock issued and substituted share awards attributable to pre-combination service	$ 191

Purchase Price Allocation (Deta

Purchase Price Allocation (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Aug. 20, 2015	Feb. 17, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 1,909,167			$ 96,352
Trulia
Business Acquisition [Line Items]
Cash and cash equivalents			$ 173,447
Accounts receivable			13,093
Prepaid expenses and other current assets			20,833
Restricted cash			6,946
Property and equipment			30,189
Other assets			434
Identifiable intangible assets			549,000
Goodwill			1,736,362
Accounts payable, accrued expenses and other current liabilities			(51,258)
Accrued compensation and benefits			(8,324)
Deferred tax liabilities	$ (139,500)
Deferred revenue			(8,300)
Long-term debt			(230,000)
Debt premium recorded in additional paid-in capital			(126,386)
Deferred tax liabilities and other long-term liabilities			(139,616)
Total preliminary estimated purchase price			$ 1,966,420
DotLoop Inc
Business Acquisition [Line Items]
Cash, cash equivalents, accounts receivable, prepaid expenses and other current assets		$ 2,149
Property and equipment and other assets		258
Identifiable intangible assets		22,500
Goodwill		86,128
Accounts payable, accrued expenses and other current liabilities, accrued compensation and benefits, and deferred revenue		(1,362)
Deferred tax liabilities		(4,135)
Total preliminary estimated purchase price		$ 105,538

Preliminary Estimated Fair Valu

Preliminary Estimated Fair Value of Identifiable Intangible Assets Acquired (Detail) - USD ($) $ in Thousands	Aug. 20, 2015	Feb. 17, 2015	Dec. 31, 2015
Trulia
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		$ 549,000
Trulia | Market Leader Trade Names and Trademarks
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		$ 2,000
Estimated Useful Life (in years)		2 years
Trulia | Customer Relationships
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		$ 92,000
Trulia | Developed Technology
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		91,000
Trulia | Advertising Relationships
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		$ 9,000
Estimated Useful Life (in years)		3 years
Trulia | MLS Home Data Feeds
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		$ 4,000
Estimated Useful Life (in years)		3 years
Trulia | Trade Names and Trademarks
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value		$ 351,000	$ 351,000
DotLoop Inc
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value	$ 22,500
DotLoop Inc | Customer Relationships
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value	10,200
DotLoop Inc | Developed Technology
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value	$ 10,700
Estimated Useful Life (in years)	3 years
DotLoop Inc | Trade Names and Trademarks
Business Acquisition [Line Items]
Total Preliminary Estimated Fair Value	$ 1,600
Estimated Useful Life (in years)	3 years
Minimum | Trulia | Customer Relationships
Business Acquisition [Line Items]
Estimated Useful Life (in years)		3 years
Minimum | Trulia | Developed Technology
Business Acquisition [Line Items]
Estimated Useful Life (in years)		3 years
Minimum | DotLoop Inc | Customer Relationships
Business Acquisition [Line Items]
Estimated Useful Life (in years)	6 years
Maximum | Trulia | Customer Relationships
Business Acquisition [Line Items]
Estimated Useful Life (in years)		7 years
Maximum | Trulia | Developed Technology
Business Acquisition [Line Items]
Estimated Useful Life (in years)		7 years
Maximum | DotLoop Inc | Customer Relationships
Business Acquisition [Line Items]
Estimated Useful Life (in years)	7 years

Pro Forma Condensed Combined Fi

Pro Forma Condensed Combined Financial Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	[1]	Dec. 31, 2014	[2]
Business Acquisition, Pro Forma Information [Abstract]
Revenue	$ 679,935		$ 577,830
Net loss	$ (91,055)		$ (83,336)
[1]	The year ended December 31, 2015 includes pro forma adjustments for $00.0 million to eliminate direct and incremental acquisition-related costs reflected in the historical financial statements, $00.0 million to eliminate share-based compensation expense attributable to substituted equity awards and to record additional share-based compensation expense attributable to substituted equity awards, $00.0 million to eliminate restructuring costs associated with the acquisition of Trulia reflected in the historical financial statements, $0.0 million to record additional amortization expense for acquired intangible assets and $0.0 million to eliminate Trulia's historical amortization of capitalized website development costs.
[2]	The year ended December 31, 2014 includes pro forma adjustments for $39.5 million to eliminate direct and incremental acquisition-related costs reflected in the historical financial statements, $18.7 million to record additional amortization expense for acquired intangible assets, $10.7 million to eliminate share-based compensation expense attributable to substituted equity awards, $6.2 million to eliminate Trulia's historical amortization of capitalized website development costs and $2.7 million to record additional rent expense.

Divestiture of Market Leader -

Divestiture of Market Leader - Additional Information (Detail) $ in Millions	Sep. 30, 2015USD ($)Employee	Dec. 31, 2015USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Employees transferred with the business to Constellation | Employee	100
Cash received at divestiture of business	$ 17
Market Leader, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Divestiture of disposal group, description		On September 2, 2015, Zillow Group, Market Leader, Inc., an indirect wholly-owned subsidiary of Zillow Group (“ML, Inc.”), Market Leader, LLC d/b/a Market Leader, LLC of Nevada, an indirect wholly-owned subsidiary of Zillow Group (together with ML, Inc., “Market Leader”), Constellation Homebuilder Systems, Corp. (“Constellation Canada”) and Constellation Web Solutions Inc. (together with Constellation Canada, the Perseus Division of Constellation), entered into an Asset Purchase Agreement (the “Asset Purchase Agreement”) pursuant to which Constellation acquired Zillow Group’s Market Leader business, including the Sharper Agent service and the Leads Direct, HouseValues and JustListed lead generation businesses, on September 30, 2015. Market Leader became part of Zillow Group through Zillow Group’s February 2015 acquisition of Trulia. Constellation acquired substantially all of the assets of the Market Leader business and assumed certain related liabilities, including Zillow Group’s Bellevue, Washington operating lease (see Note 16). In connection with the divestiture, Market Leader’s approximately 100 employees transferred with the business to Constellation. The total sales price of approximately $22.7 million includes $17.0 million that was paid in cash at closing and approximately $5.7 million for the estimated amount to be received by Zillow Group from Constellation on December 29, 2015 upon the expiration of a holdback period to satisfy any purchase price adjustments and/or indemnification claims.
Total sales price of disposal group	22.6
Market Leader, Inc. | Prepaid Expenses and Other Current Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total sales price of disposal group	$ 5.6
Market Leader, Inc. | Loss on Divestiture of Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loss recorded related to the divestiture of disposal group		$ (4.4)

Schedule of Aggregate Carrying

Schedule of Aggregate Carrying Amounts of Major Classes of Assets and Liabilities (Detail) - Market Leader, Inc. $ in Thousands	Sep. 30, 2015USD ($)
Assets
Prepaid expenses and other current assets	$ 501
Property and equipment, net	5,764
Goodwill	9,209
Intangible assets, net	17,161
Total assets	32,635
Liabilities
Current liabilities	2,278
Other long-term liabilities	3,771
Total liabilities	$ 6,049

Change in Goodwill (Detail)

Change in Goodwill (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Goodwill [Line Items]
Balance as of December 31, 2014	$ 96,352
Reduction of goodwill in connection with the divestitures of businesses	(9,675)
Balance as of December 31, 2015	1,909,167
Trulia
Goodwill [Line Items]
Goodwill recorded in connection with the acquisition	1,736,362
DotLoop Inc
Goodwill [Line Items]
Goodwill recorded in connection with the acquisition	$ 86,128

Intangible Assets (Detail)

Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Cost	$ 264,261	$ 50,696
Accumulated Amortization	(60,496)	(23,939)
Net	203,765	26,757
Purchased Content
Finite-Lived Intangible Assets [Line Items]
Cost	37,581	24,615
Accumulated Amortization	(19,649)	(13,904)
Net	17,932	10,711
Developed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	108,295	13,595
Accumulated Amortization	(19,515)	(5,321)
Net	88,780	8,274
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	103,425	9,225
Accumulated Amortization	(16,204)	(3,387)
Net	87,221	5,838
Trade Names and Trademarks
Finite-Lived Intangible Assets [Line Items]
Cost	4,860
Accumulated Amortization	(2,212)
Net	2,648
Advertising Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	9,000
Accumulated Amortization	(2,598)
Net	6,402
MLS Home Data Feeds
Finite-Lived Intangible Assets [Line Items]
Cost	1,100
Accumulated Amortization	(318)
Net	$ 782
Trademarks
Finite-Lived Intangible Assets [Line Items]
Cost		3,261
Accumulated Amortization		(1,327)
Net		$ 1,934

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Amortization of website development costs and intangible assets included in technology and development	$ 63,189	$ 29,487	$ 19,791
Trulia
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible asset	351,000
Technology and Development
Finite-Lived Intangible Assets [Line Items]
Amortization of website development costs and intangible assets included in technology and development	$ 39,300	$ 11,100	$ 7,600

Estimated Future Amortization E

Estimated Future Amortization Expense for Intangible Assets (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,016	$ 46,377
2,017	44,090
2,018	37,727
2,019	32,906
2,020	32,415
All future years	43,894
Total future amortization expense	$ 237,409

Summary of accrued expenses and

Summary of accrued expenses and other current liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities [Line Items]
Total accrued expenses and other current liabilities	$ 43,047	$ 16,883
Accrued marketing and advertising
Accrued Expenses and Other Current Liabilities [Line Items]
Total accrued expenses and other current liabilities	9,663	1,509
Accrued purchased content
Accrued Expenses and Other Current Liabilities [Line Items]
Total accrued expenses and other current liabilities	8,385
Accrued legal fees
Accrued Expenses and Other Current Liabilities [Line Items]
Total accrued expenses and other current liabilities	7,784	3,755
Merger consideration payable to former stockholders of StreetEasy, Inc.
Accrued Expenses and Other Current Liabilities [Line Items]
Total accrued expenses and other current liabilities	5,317	5,317
Other accrued expenses and other current liabilities
Accrued Expenses and Other Current Liabilities [Line Items]
Total accrued expenses and other current liabilities	$ 11,898	$ 6,302

Convertible Senior Notes - Addi

Convertible Senior Notes - Additional Information (Detail)	Feb. 17, 2015USD ($)	Dec. 31, 2015USD ($)Financial_Covenantsd$ / shares
Debt Instrument [Line Items]
Common stock exchange ratio	0.444
Class A Common Stock | Stock Split [Member]
Debt Instrument [Line Items]
Debt instrument, conversion rate principal amount		$ 1,000
Debt instrument, conversion rate shares		41.4550
Initial conversion price | $ / shares		$ 24.12
2.75% Convertible Senior Notes Due 2020
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount	$ 230,000,000	$ 230,000,000
Debt instrument, due date		Dec. 15, 2020
Debt instrument, interest rate stated percentage	2.75%
Debt instrument, frequency of period payment		Semi-annually on June 15 and December 15
Debt instrument, conversion rate principal amount		$ 1,000
Debt instrument, conversion rate shares		27.8303
Repurchase price percentage of principal amount		100.00%
Number of financial covenants | Financial_Covenants		0
Debt instrument, redemption period start date		Dec. 20, 2018
Interest expense		$ 5,500,000
Accrued interest		300,000
Fair value of convertible notes		272,900,000
Debt instrument carrying value		$ 230,000,000
2.75% Convertible Senior Notes Due 2020 | Class A Common Stock
Debt Instrument [Line Items]
Debt instrument, conversion rate shares		12.3567
Common stock exchange ratio		0.444
Initial conversion price | $ / shares		$ 80.93
Debt instrument, convertible threshold percentage		130.00%
Debt instrument, convertible threshold trading days | d		20
Debt instrument, convertible threshold consecutive trading days		30 days

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Income Tax [Line Items]
Related income tax liability	$ 0	$ 0	$ 0
Income tax benefit	4,645,000		4,111,000
Increase/decrease in valuation allowance	125,500,000	9,900,000
Unrecognized income tax accrued interest and penalties	0
Unrecognized tax benefits	$ 13,980,000	6,493,000	$ 5,123,000	$ 1,255,000
Earliest Tax Year
Schedule Of Income Tax [Line Items]
Income tax year open for audit	2,012
Latest Tax Year
Schedule Of Income Tax [Line Items]
Income tax year open for audit	2,015
Share Based Compensation Liability
Schedule Of Income Tax [Line Items]
Net operating loss carryforwards	$ 304,000,000
Research And Development
Schedule Of Income Tax [Line Items]
Net operating loss carryforwards	$ 17,200,000	6,500,000
Tax credit carryforwards expiration year	2,025
Federal
Schedule Of Income Tax [Line Items]
Net operating loss carryforwards	$ 735,200,000	358,600,000
State
Schedule Of Income Tax [Line Items]
Net operating loss carryforwards	$ 11,600,000	$ 7,200,000

Components of Income Tax Benefi

Components of Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal	$ 2,838	$ 3,783
State	1,807	328
Deferred income tax benefit	$ 4,645	$ 4,111

Reconciliation of Federal Statu

Reconciliation of Federal Statutory Rate and Effective Tax rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax expense at federal statutory rate	(35.00%)	(34.00%)	(34.00%)
State income taxes, net of federal tax benefit	(2.30%)	(1.50%)	(5.80%)
Nondeductible expenses	2.80%	15.30%	3.10%
Share-based compensation	1.20%	0.70%	0.20%
Research and development credits	(4.10%)	(3.20%)	(23.30%)
Divestiture of businesses	2.30%
Other	(1.00%)
Valuation allowance	33.10%	22.70%	35.00%
Effective tax rate	(3.00%)	0.00%	(24.80%)

Deferred Tax Assets and Liabili

Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 162,521	$ 25,665
Share-based compensation	45,969	12,680
Goodwill	825	1,355
Depreciation and amortization	3,090
Start-up and organizational costs	369	430
Research and development credits	21,157	6,493
Other tax credits	1,358
Accruals and reserves	3,338	2,339
Deferred rent	5,228	4,248
Other deferred tax assets	550	167
Total deferred tax assets	244,405	53,377
Deferred tax liabilities:
Website and software development costs	(13,851)	(7,263)
Intangibles	(200,082)	(6,052)
Other deferred tax liabilities	(52)
Depreciation and amortization		(2,838)
Net deferred tax assets before valuation allowance	30,420	37,224
Less: valuation allowance	(162,715)	$ (37,224)
Net deferred tax assets (liabilities)	$ (132,295)

Changes in Unrecognized Tax Ben

Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Unrecognized tax benefits beginning balance	$ 6,493	$ 5,123	$ 1,255
Gross decreases - prior period tax positions		(576)
Gross increases - prior and current period tax positions	3,577		3,868
Gross increases - assumed in connection with February 2015 acquisition of Trulia	3,910
Unrecognized tax benefits ending balance	$ 13,980	6,493	$ 5,123
Gross increases - current period tax positions		$ 1,946

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail)	Aug. 14, 2015shares	Aug. 31, 2013USD ($)$ / sharesshares	Dec. 31, 2015Vote$ / sharesshares	Dec. 31, 2014$ / sharesshares	Dec. 31, 2013shares
Class of Stock [Line Items]
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
Net proceeds from issuance of common stock | $		$ 253,900,000
Stock split description			Outstanding equity awards to purchase or acquire shares of Class A common stock were proportionately adjusted to relate to one share of Class A common stock and two shares of Class C capital stock for each share of Class A common stock subject to the awards as of the record date, and the exercise prices of any such awards were also proportionately allocated between Class A common stock and Class C capital stock.
Stock split ratio	3
Class A Common Stock
Class of Stock [Line Items]
Common stock holders voting right | Vote			1
Conversion of common stock conversion ratio			1
Number of common stock issued			0
Issuance of Class A common stock, shares		3,253,522
Net proceeds from issuance of common stock | $		$ 0
Common stock, par value after Class C Stock Split | $ / shares			$ 0.0001	$ 0.0001
Class A Common Stock | Over-Allotment Option
Class of Stock [Line Items]
Issuance of Class A common stock, shares		753,522
Class A Common Stock | Private Placement
Class of Stock [Line Items]
Issuance of Class A common stock, shares		2,523,486
Class A common stock at an offering price | $ / shares		$ 82
Class B Common Stock
Class of Stock [Line Items]
Common stock holders voting right | Vote			10
Number of common stock converted			0	251,445	993,634
Common stock, par value after Class C Stock Split | $ / shares			$ 0.0001	$ 0.0001
Class C Capital Stock
Class of Stock [Line Items]
Common stock holders voting right | Vote			0
Dividend declaration date			Jul. 21, 2015
Dividend record date			Jul. 31, 2015
Dividend payable date			Aug. 14, 2015
Distribution of shares for each class of common stock held as of record date	2		2
Stock split description			On August 14, 2015, Zillow Group completed a stock dividend in the form of two shares of Class C capital stock for each share of Class A common stock and Class B common stock outstanding as of July 31, 2015. The stock dividend had the effect of a 3-for-1 stock split.
Common stock, par value after Class C Stock Split | $ / shares			$ 0.0001	$ 0.0001

Common and Capital Stock Reserv

Common and Capital Stock Reserved for Future Issuance (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Total	36,637,349	26,011,363
Class B Common Stock
Class of Stock [Line Items]
Shares issuable upon conversion of outstanding Class B common stock	6,217,447	6,217,447
Option Awards
Class of Stock [Line Items]
Option awards outstanding	27,126,374	17,399,292
Option Awards | 2011 Plan
Class of Stock [Line Items]
Class A common stock and Class C capital stock available for grant under 2011 Plan	688,014	2,017,818
Restricted Stock Units
Class of Stock [Line Items]
Restricted stock units outstanding	2,605,514	376,806

Share-Based Awards - Additional

Share-Based Awards - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share based awards description	In connection with the Class C Stock Split discussed in Note 13 above, all outstanding equity awards under each of the plans described below (collectively, the “Plans”) as of the record date were proportionately adjusted to relate to one share of Class A common stock and two shares of Class C capital stock for each share of Class A common stock subject to the awards as of the record date (the “Split Adjustment”). The original exercise prices of outstanding stock options and stock appreciation rights were proportionally allocated between shares of Class A common stock and Class C capital stock, based on the ratio of the when-issued trading prices of the Class A common stock and the Class C capital stock during the ten trading days prior to and including the payment date of the Class C Stock Split. In connection with the Split Adjustment, each stock option and stock appreciation right is independently exercisable (to the extent vested) for shares of Class A common stock and shares of Class C capital stock so that, in effect, for each share of Class A common stock subject to the option or stock appreciation right prior to the Class C Stock Split, the Split Adjustment resulted in a stock option to purchase one share of Class A common stock and a stock option to purchase two shares of Class C capital stock. Each such adjusted equity award otherwise has the same terms and conditions, including the vesting schedule and term, as the original equity award prior to the Split Adjustment.

Share-Based Awards - Zillow Gro

Share-Based Awards - Zillow Group, Inc. Incentive Plan - Additional Information (Detail) - shares	Jun. 11, 2015	Feb. 28, 2015	Dec. 31, 2015	Aug. 14, 2015	Aug. 13, 2015	Jun. 10, 2015
Restricted Stock Units | Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%	50.00%
Vesting period		3 years
Restricted Stock Units | Vesting After 6 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		12.50%
Vesting period		3 years 6 months
Amended and Restated 2011 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance	1,500,000
Number of shares authorized for issuance				5,300,000		3,800,000
Total number of shares available for issuance under awards			15,900,000		5,300,000
Increase in number of shares of common stock available for issuance percentage			3.50%
Increase in number of shares of common stock available for issuance			10,500,000		3,500,000
Amended and Restated 2011 Incentive Plan | Class C Capital Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares available for issuance under awards			1,953,950
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price per share fixed			100.00%
2011 Plan | Option Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period			7 years
Share based compensation arrangement by share based payment, award minimum exercisable period			3 months
Share based compensation arrangement by share based payment, award maximum exercisable period			12 months
Options vesting rights			Options granted under the 2011 Plan are typically granted with seven-year terms and typically vest 25% after 12 months and ratably thereafter over the next 36 months, though certain options have been granted with longer terms and vesting schedules.
2011 Plan | Option Awards | Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
2011 Plan | Option Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period			10 years
Vesting period			36 months
2011 Plan | Option Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			12 months
2011 Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting rights			Vest either 25% after 12 months and quarterly thereafter over the next three years or 12.5% after 6 months and quarterly thereafter for the next 3.5 years.
2011 Plan | Restricted Stock Units | Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
2011 Plan | Restricted Stock Units | Vesting After 6 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			12.50%
2011 Plan | Restricted Stock Units | Maximum | Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
2011 Plan | Restricted Stock Units | Maximum | Vesting After 6 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years 6 months
2011 Plan | Restricted Stock Units | Minimum | Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			12 months
2011 Plan | Restricted Stock Units | Minimum | Vesting After 6 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			6 months

Share-Based Awards - Trulia Sto

Share-Based Awards - Trulia Stock Incentive Plan - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015
Trulia 2012 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Exercise price per share fixed	100.00%
Trulia 2005 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Options vesting rights	Certain options vest monthly over two to four years
Trulia 2005 Stock Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	12 months
Trulia 2005 Stock Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	36 months
Trulia 2005 Stock Incentive Plan | Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%

Summary of Option Award and Sto

Summary of Option Award and Stock Appreciation Rights Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Beginning Balance	17,399,292
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Assumed Trulia options and stock appreciation rights in connection with February 2015 acquisition of Trulia	3,159,765
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Granted	11,438,095
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Exercised	(2,732,767)
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Forfeited or cancelled	(2,138,011)
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Ending Balance	27,126,374	17,399,292
Number of Shares Subject to Existing Option Awards and Stock Appreciation Rights, Vested and exercisable, Ending balance	9,470,685
Weighted-Average Exercise Price Per Share, Beginning Balance	$ 18.12
Weighted-Average Exercise Price Per Share, Assumed Trulia options and stock appreciation rights in connection with February 2015 acquisition of Trulia	13.79
Weighted-Average Exercise Price Per Share, Granted	31.45
Weighted-Average Exercise Price Per Share, Exercised	8.99
Weighted-Average Exercise Price Per Share, Forfeited or cancelled	28.37
Weighted-Average Exercise Price Per Share, Ending Balance	23.35	$ 18.12
Weighted-Average Exercise Price Per Share, Vested and exercisable	$ 14.44
Weighted-Average Remaining Contractual Life (Years)	5 years 11 months 16 days	5 years 3 months 26 days
Weighted-Average Remaining Contractual Life (Years), Vested and exercisable	3 years 11 months 5 days
Aggregate Intrinsic Value	$ 156,025	$ 311,040
Aggregate Intrinsic Value Vested, and exercisable	$ 112,923

Share-Based Awards - Option Awa

Share-Based Awards - Option Awards and Stock Appreciation Rights - Additional Information (Detail) - USD ($)	Aug. 20, 2015	Mar. 31, 2015	Jan. 31, 2013	Feb. 28, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted					11,438,095
Number of options granted, weighted-average exercise price					$ 31.45
Fair value of options granted					$ 13.77	$ 14.78	$ 7.09
Share-based compensation					$ 120,073,000	$ 34,085,000	$ 23,436,000
Share-based compensation arrangement by share-based payment award, option awards, exercises in period, total intrinsic value					67,300,000	124,000,000	114,400,000
Option Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost					$ 203,900,000
Unrecognized compensation cost expected recognition period					3 years 6 months
Fair value of options					$ 59,900,000	18,900,000	10,600,000
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost					$ 203,900,000
Unrecognized compensation cost expected recognition period					3 years 6 months
Total grant date fair value					$ 59,900,000	$ 18,900,000	$ 10,600,000
Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option awards of Class A common stock and Class C capital stock granted				3,450,000
Fair value of option awards granted				$ 62,800,000
Expected dividend				$ 0
Expected volatility				52.00%
Risk-free interest rate				1.76%
Weighted-average expected life				6 years 9 months 18 days
Options vesting rights					One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the first anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable four years from the vesting commencement date. One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the two-year anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable five years from the vesting commencement date. One-sixteenth of the total number of shares subject to the option awards will vest and become exercisable on the three-year anniversary of the vesting commencement date. An additional 1/192nd of the total number of shares subject to the option awards will vest and become exercisable monthly thereafter over the next three years so that this portion of the award will be vested and exercisable six years from the vesting commencement date.
Expiration period				10 years
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option awards of Class A common stock and Class C capital stock granted		47,175
Expected volatility		57.00%
Risk-free interest rate		1.01%
Weighted-average expected life		3 years 6 months
Fair value of options granted		$ 15.90
Share-based compensation					$ 800,000
Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option awards of Class A common stock and Class C capital stock granted			1,500,000
Expected volatility			51.00%
Risk-free interest rate			0.70%
Weighted-average expected life			7 years 3 months 18 days
Fair value of options granted			$ 6.33
DotLoop Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted					199,779
Number of options granted, weighted-average exercise price					$ 9.29
DotLoop Inc | Option Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	55.00%
Risk-free interest rate	1.25%
Weighted-average expected life	4 years 3 months 11 days

Fair Value of Options Granted,

Fair Value of Options Granted, Excluding Stock Option Grant Program of Nonemployee Directors and Executives, Estimated at Date of Grant Using Black Scholes Merton Option Pricing Model (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	54.00%	53.00%	50.00%
Expected volatility, maximum	56.00%	57.00%	54.00%
Expected dividend yield	0.00%	0.00%	0.00%
Risk-free interest rate, minimum	1.03%	1.37%	0.70%
Risk-free interest rate, maximum	1.48%	1.55%	1.27%
Weighted-average fair value of options granted	$ 13.77	$ 14.78	$ 7.09
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life	3 years 6 months	4 years 6 months 29 days	4 years 6 months 29 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life	4 years 6 months 29 days

Summary of Restricted Stock Awa

Summary of Restricted Stock Award Activity (Detail) - Restricted Stock	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Restricted Stock Units
Unvested outstanding, beginning balance | shares	260,505
Granted | shares	4,173
Vested | shares	(233,732)
Forfeited or cancelled | shares	0
Unvested outstanding, ending balance | shares	30,946
Weighted-Average Grant-Date Fair Value
Unvested outstanding, beginning balance | $ / shares	$ 10.75
Granted | $ / shares	40.45
Vested | $ / shares	11.07
Forfeited or cancelled | $ / shares	0
Unvested outstanding, ending balance | $ / shares	$ 12.35

Share-Based Awards - Restricted

Share-Based Awards - Restricted Stock Awards - Additional Information (Detail) - Restricted Stock - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted stock vested	$ 2.6	$ 4.5	$ 3.4
Total unrecognized compensation cost	$ 0.4
Unrecognized compensation cost expected recognition period	9 months 18 days

Summary of Restricted Stock Uni

Summary of Restricted Stock Units Activity (Detail) - Restricted Stock Units - $ / shares	1 Months Ended	12 Months Ended
	Feb. 28, 2015	Dec. 31, 2015
Restricted Stock Units
Unvested outstanding, beginning balance		376,806
Assumed Trulia restricted stock units in connection with February 2015 acquisition of Trulia		3,798,957
Granted	82,077	1,354,185
Vested		(1,899,531)
Forfeited or cancelled		(1,024,903)
Unvested outstanding, ending balance		2,605,514
Weighted-Average Grant-Date Fair Value
Unvested outstanding, beginning balance		$ 28.56
Assumed Trulia restricted stock units in connection with February 2015 acquisition of Trulia		36.38
Granted		28.55
Vested		31.74
Forfeited or cancelled		31.12
Unvested outstanding, ending balance		$ 32.36

Share-Based Awards - Restrict92

Share-Based Awards - Restricted Stock Units - Additional Information (Detail) - Restricted Stock Units - USD ($) $ in Millions	Apr. 30, 2015	Aug. 31, 2015	Feb. 28, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			82,077	1,354,185
Accelerated vesting period received by employee				12 months
Terms of restricted stock unit award				In the event of termination of service or employment by Zillow Group without cause or upon the resignation by such employee for good reason, the employee will receive an additional 12 months’ accelerated vesting of the then outstanding restricted stock units, except that in the event of such a termination in connection with a change in control, the employee will receive 50% accelerated vesting of the then outstanding restricted stock units. The employee will be entitled to receive one share of Class A common stock and two shares of Class C capital stock for each then outstanding restricted stock unit that becomes vested. The grant date fair value of the restricted stock units
Fair value of restricted shares issued				$ 3
Total fair value of restricted stock vested				67.3	$ 5.1	$ 10.5
Total unrecognized compensation cost				$ 69
Unrecognized compensation cost expected recognition period				2 years 7 months 6 days
Retention Plan | Trulia
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting commencement date of restricted shares				Feb. 18, 2015
Options vesting rights				12.5% of the retention restricted stock units vested approximately 6 months after the vesting commencement date of February 18, 2015, and the remaining retention restricted stock units vest quarterly thereafter for approximately 3.5 years, subject to the recipient's continued full-time employment or service to Zillow Group
Total fair value of restricted stock vested	$ 10.2
Retention Plan | Trulia | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	6 months
Retention Plan | Trulia | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years 6 months
Retention Plan | Class A Common Stock and Class C Capital Stock | Trulia
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	316,074
Retention Bonus Plan Member | DotLoop Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted stock vested				$ 4.5
Vesting After 12 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			50,202
Vesting percentage			25.00%	50.00%
Vesting period			3 years
Vesting commencement date of restricted shares			Feb. 17, 2016
Vesting After 6 Months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			31,875
Vesting percentage			12.50%
Vesting period			3 years 6 months
Vesting commencement date of restricted shares			Aug. 17, 2015
Vesting After 6 Months | Retention Plan | Trulia
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	12.50%
For 178,428 of Restricted Stock Units | Retention Bonus Plan Member | DotLoop Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		178,428
Vesting percentage		25.00%
Vesting period		3 years
Vesting commencement date of restricted shares				Aug. 20, 2016
Options vesting rights				25% of the restricted stock units vest on August 20, 2016, and the remaining restricted stock units vest quarterly thereafter over the next three years.
For 173,761 of Restricted Stock Units | Retention Bonus Plan Member | DotLoop Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		173,761
Vesting percentage		50.00%
Vesting period		3 years
Vesting commencement date of restricted shares				Aug. 20, 2016
Options vesting rights				50% of the restricted stock units vest on August 21, 2016, and the remaining restricted stock units vest quarterly thereafter for the next three years.
Total fair value of restricted stock vested				$ 4.4

Effects of Share Based Compensa

Effects of Share Based Compensation in Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation	$ 120,073	$ 34,085	$ 23,436
Cost of Revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation	4,694	1,844	737
Sales and Marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation	25,391	7,320	10,969
Technology and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation	26,849	11,681	4,660
General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation	48,280	$ 13,240	$ 7,070
Restructuring Costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation	$ 14,859

Share-Based Awards - Share-Base

Share-Based Awards - Share-Based Compensation Expense - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 120,073	$ 34,085	$ 23,436
Sales and Marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	25,391	7,320	10,969
Technology and Development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	26,849	11,681	4,660
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	48,280	$ 13,240	$ 7,070
February 2015 Restructuring Plan | Sales and Marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	1,800
February 2015 Restructuring Plan | Technology and Development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	1,400
February 2015 Restructuring Plan | General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 6,700

Antidilutive Securities Exclude

Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class A Common Stock and Class C Capital Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Class A common stock and Class C capital stock equivalents excluded from calculations of diluted net loss per share	16,925	9,063	10,050
Class A Common Stock and Class C Capital Stock | Option Awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Class A common stock and Class C capital stock equivalents excluded from calculations of diluted net loss per share	6,751	8,709	9,537
Class A Common Stock and Class C Capital Stock | Restricted Stock Awards and Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Class A common stock and Class C capital stock equivalents excluded from calculations of diluted net loss per share	639	354	513
Class A Common Stock | 2.75% Convertible Senior Notes Due 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Class A common stock and Class C capital stock equivalents excluded from calculations of diluted net loss per share	9,535

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)

Nov. 30, 2012ft²

May. 31, 2015ft²

Nov. 30, 2014ft²

Jul. 31, 2014ft²

Nov. 30, 2010Patent

Sep. 30, 2010Patent

Mar. 31, 2010Patent

Dec. 31, 2015USD ($)ft²

Dec. 31, 2014USD ($)

Dec. 31, 2013USD ($)

Jul. 31, 2015ft²

Feb. 17, 2015ft²

Feb. 28, 2014ft²

Apr. 30, 2012ft²

Mar. 01, 2011ft²

Property Subject to or Available for Operating Lease [Line Items]

Rent expense | $

$ 14,900,000

$ 7,500,000

$ 4,100,000

Minimum rentals to be received in future under noncancelable subleases | $

4,300,000

Non-cancelable purchase commitments | $

99,671,000

Outstanding surety bonds | $

$ 3,400,000

$ 0

Number of patents infringed | Patent

3

Acquisition date

Feb. 17, 2015

Trulia

Property Subject to or Available for Operating Lease [Line Items]

Acquisition date

Feb. 17, 2015

Seattle, Washington

Property Subject to or Available for Operating Lease [Line Items]

Outstanding letters of credit | $

$ 1,800,000

Seattle, Washington | Operating Lease

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

155,042

Additional area of office space leased | ft²

113,470

Lease agreement term

145 months

New York

Property Subject to or Available for Operating Lease [Line Items]

Outstanding letters of credit | $

$ 1,100,000

New York | Operating Lease

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

39,900

Lease agreement term

124 months

New York | Sublet

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

6,650

Denver, Colorado

Property Subject to or Available for Operating Lease [Line Items]

Outstanding letters of credit | $

$ 1,100,000

Denver, Colorado | Operating Lease | Trulia

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

65,000

Lease agreement term

84 months

Irvine, California | Operating Lease

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

60,000

Lease agreement term

120 months

Bellevue, Washington

Property Subject to or Available for Operating Lease [Line Items]

Outstanding letters of credit | $

$ 1,500,000

Bellevue, Washington | Operating Lease | Trulia

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

72,000

San Francisco, California

Property Subject to or Available for Operating Lease [Line Items]

Outstanding letters of credit | $

$ 4,600,000

San Francisco, California | Operating Lease

Property Subject to or Available for Operating Lease [Line Items]

Rentable area of the premises | ft²

18,353

79,000

Additional area of office space leased | ft²

8,311

26,620

Lease agreement term

72 months

107 months

LendingTree, LLC

Property Subject to or Available for Operating Lease [Line Items]

Number of patents infringed | Patent

2

Allegations and asserted defenses

In March 2014, a federal jury found that Zillow does not infringe the patents and that the patents asserted by LendingTree are invalid.

Smarter Agent

Property Subject to or Available for Operating Lease [Line Items]

Number of patents-in-suit | Patent

3

Smarter Agent | Diverse Solutions, Inc

Property Subject to or Available for Operating Lease [Line Items]

Acquisition date

Oct. 31, 2011

Smarter Agent | StreetEasy, Inc.

Property Subject to or Available for Operating Lease [Line Items]

Acquisition date

Aug. 26, 2013

Smarter Agent | HotPads, Inc.

Property Subject to or Available for Operating Lease [Line Items]

Acquisition date

Dec. 14, 2012

Future Minimum Payments for All

Future Minimum Payments for All Operating Leases (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 17,885
2,017	21,702
2,018	23,222
2,019	21,909
2,020	22,439
All future years	80,953
Total future minimum lease payments	$ 188,110

Purchase Commitments for Conten

Purchase Commitments for Content Related to Mobile Applications and Websites (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 34,330
2,017	34,841
2,018	14,000
2,019	6,000
2,020	6,000
2,021	4,500
Total future purchase commitments	$ 99,671

Restructuring - Additional Info

Restructuring - Additional Information (Detail) - February 2015 Restructuring Plan $ in Millions	Feb. 17, 2015Employee	Dec. 31, 2015USD ($)	Dec. 31, 2014Employee
Restructuring Cost and Reserve [Line Items]
Reduction of market leader head count | Employee	350		80
Restructuring charge		$ 35.6
Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charge		8.2
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charge		12.2
Noncash Expenses Relating to Employee Benefit
Restructuring Cost and Reserve [Line Items]
Restructuring charge		14.9
Leasehold improvements | Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs for contract termination costs		$ 4

Summary of Accrued Restructurin

Summary of Accrued Restructuring Costs (Detail) - USD ($) $ in Thousands	10 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 35,551
Trulia Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Accrued restructuring costs beginning balance	$ 2,761
Restructuring costs	13,756
Cash payments	(14,248)
Change in estimate	2,511
Restructuring liabilities transferred in connection with September 2015 divestiture of Market Leader	(4,611)
Accrued restructuring costs ending balance	169	169
One-Time Termination Benefits | Trulia Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Accrued restructuring costs beginning balance	81
Restructuring costs	11,933
Cash payments	(12,111)
Change in estimate	97
Contract Termination Costs | Trulia Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Accrued restructuring costs beginning balance	2,544
Restructuring costs	1,508
Cash payments	(1,557)
Change in estimate	2,285
Restructuring liabilities transferred in connection with September 2015 divestiture of Market Leader	(4,611)
Accrued restructuring costs ending balance	169	$ 169
Other Associated Costs | Trulia Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Accrued restructuring costs beginning balance	136
Restructuring costs	315
Cash payments	(580)
Change in estimate	$ 129

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2015	Dec. 31, 2015
Mr.Richard Barton
Related Party Transaction [Line Items]
Payment of filing fees	$ 0.3
Reimbursement of costs incurred		$ 0.2
Mr.Lloyd Frink
Related Party Transaction [Line Items]
Payment of filing fees	$ 0.1
Reimbursement of costs incurred		$ 0.2

Self-Insurance - Additional Inf

Self-Insurance - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)
Insurance [Line Items]
Minimum amount of individual claim under self insurance plan	$ 100,000
Liability for self-insured claims included in accrued compensation and benefits	$ 500,000
Minimum
Insurance [Line Items]
Percentage of cumulative medical claim under self insurance plan	125.00%

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Company's expense related to its defined contribution 401(k) retirement plans	$ 4,200,000	$ 0	$ 0
Maximum
Defined Benefit Plan Disclosure [Line Items]
Company's contribution based on employee contribution	1.50%
Maximum | Trulia
Defined Benefit Plan Disclosure [Line Items]
Company's contribution based on employee contribution	4.00%

Segment Information and Reve104

Segment Information and Revenue - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015Segment
Segment Reporting [Abstract]
Number of reportable segment	1

Revenue Categories (Detail)

Revenue Categories (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Total Marketplace revenue	$ 555,904	$ 267,242	$ 154,713
Display revenue	88,773	58,651	42,832
Total revenue	644,677	325,893	197,545
Real Estate Revenue
Revenues:
Total Marketplace revenue	482,092	239,039	132,901
Mortgages Revenue
Revenues:
Total Marketplace revenue	44,263	$ 28,203	$ 21,812
Market Leader Revenue
Revenues:
Total Marketplace revenue	$ 29,549

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Millions	Feb. 02, 2016USD ($)
Subsequent Event | Naked Apartments Inc
Subsequent Event [Line Items]
Business acquisition purchase price in cash	$ 13