Zillow (ZG) 10-Q 8 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2014	Apr. 30, 2014
		Class A Common Stock	Class B Common Stock
Document Information [Line Items]	'	'	'
Document Type	'10-Q	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Mar-14	'	'
Document Fiscal Year Focus	'2014	'	'
Document Fiscal Period Focus	'Q1	'	'
Trading Symbol	'Z	'	'
Entity Registrant Name	'ZILLOW INC	'	'
Entity Central Index Key	'0001334814	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	33,559,096	6,267,447

Condensed_Balance_Sheets

Condensed Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$153,654	$201,760
Short-term investments	155,760	93,531
Accounts receivable, net of allowance for doubtful accounts of $2,187 and $1,850 at March 31, 2014 and December 31, 2013, respectively	14,859	15,234
Prepaid expenses and other current assets	6,817	4,987
Total current assets	331,090	315,512
Long-term investments	137,949	142,435
Property and equipment, net	31,114	27,408
Goodwill	93,213	93,213
Intangible assets, net	27,740	29,149
Other assets	436	346
Total assets	621,542	608,063
Current liabilities:	'	'
Accounts payable	6,403	4,724
Accrued expenses and other current liabilities	13,845	11,377
Accrued compensation and benefits	5,510	4,440
Deferred revenue	12,140	12,298
Deferred rent, current portion	632	546
Total current liabilities	38,530	33,385
Deferred rent, net of current portion	7,493	6,882
Commitments and contingencies (Note 10)	'	'
Shareholders' equity:	'	'
Preferred stock	'	'
Additional paid-in capital	665,895	651,913
Accumulated deficit	-90,380	-84,121
Total shareholders' equity	575,519	567,796
Total liabilities and shareholders' equity	621,542	608,063
Class A Common Stock	'	'
Shareholders' equity:	'	'
Common stock	3	3
Class B Common Stock	'	'
Shareholders' equity:	'	'
Common stock	$1	$1

Condensed_Balance_Sheets_Paren

Condensed Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Accounts receivable, allowance for doubtful accounts	$2,187	$1,850
Preferred stock, par value	$0.00	$0.00
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	$0.00	$0.00
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares issued	33,462,773	32,934,074
Common stock, shares outstanding	33,462,773	32,934,074
Class B Common Stock	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	6,267,447	6,468,892
Common stock, shares outstanding	6,267,447	6,468,892

Condensed_Statements_of_Operat

Condensed Statements of Operations (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Income Statement [Abstract]	'		'
Revenue	$66,243		$38,966
Costs and expenses:	'		'
Cost of revenue (exclusive of amortization)	6,164	[1]	4,130	[1]
Sales and marketing	34,898		19,794
Technology and development	16,970		10,611
General and administrative	14,689		8,233
Total costs and expenses	72,721		42,768
Loss from operations	-6,478		-3,802
Other income	219		55
Net loss	($6,259)		($3,747)
Net loss per share - basic and diluted	($0.16)		($0.11)
Weighted-average shares outstanding - basic and diluted	39,322		33,770
[1]	Amortization of website development costs and intangible assets included in technology and development $ 6,784 $ 4,208

Condensed_Statements_of_Operat1

Condensed Statements of Operations (Parenthetical) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]	'	'
Amortization of website development costs and intangible assets included in technology and development	$6,784	$4,208

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Operating activities	'	'
Net loss	($6,259)	($3,747)
Adjustments to reconcile net loss to net cash provided by operating activities:	'	'
Depreciation and amortization	8,074	4,779
Share-based compensation expense	7,132	4,146
Loss on disposal of property and equipment	235	495
Bad debt expense	635	414
Deferred rent	697	198
Amortization of bond premium	812	69
Changes in operating assets and liabilities:	'	'
Accounts receivable	-260	-1,258
Prepaid expenses and other assets	-1,920	-1,768
Accounts payable	1,679	1,241
Accrued expenses	3,538	-1,710
Deferred revenue	-158	-570
Net cash provided by operating activities	14,205	2,289
Investing activities	'	'
Proceeds from maturities of investments	44,539	5,000
Purchases of investments	-103,094	-23,809
Purchases of property and equipment	-7,872	-5,944
Purchases of intangible assets	-1,147	-685
Net cash used in investing activities	-67,574	-25,438
Financing activities	'	'
Proceeds from exercise of Class A common stock options	5,263	5,057
Net cash provided by financing activities	5,263	5,057
Net decrease in cash and cash equivalents during period	-48,106	-18,092
Cash and cash equivalents at beginning of period	201,760	150,040
Cash and cash equivalents at end of period	153,654	131,948
Noncash transactions:	'	'
Capitalized share-based compensation	1,586	777
Write-off of fully depreciated property and equipment	$1,498	$485

Organization_and_Description_o

Organization and Description of Business	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Organization and Description of Business	'
	Note 1.	Organization and Description of Business
	Zillow, Inc. was incorporated as a Washington corporation effective December 13, 2004, and we launched the initial version of our website, Zillow.com, in February 2006. Zillow 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. In addition to our living database of homes, accessible on Zillow.com, we also own and operate Zillow Mobile, our suite of home-related mobile applications, Zillow Mortgage Marketplace, where borrowers connect with lenders to find loans and get competitive mortgage rates, Zillow Digs, our home improvement marketplace where consumers can find visual inspiration and local cost estimates, Zillow Rentals, a marketplace and suite of tools for rental professionals, Postlets, Diverse Solutions, Agentfolio, Mortech, HotPads and StreetEasy. Zillow provides products and services to help consumers through every stage of homeownership – buying, selling, renting, borrowing and remodeling.
	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 in any of the following areas could have a significant negative 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; management of our growth; acquisitions and investments; qualified employees and key personnel; protection of our brand and intellectual property; changes in government regulation affecting our business; 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_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	Note 2.	Summary of Significant Accounting Policies
	Basis of Presentation
	The accompanying condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these interim condensed financial statements should be read in conjunction with the audited financial statements and accompanying notes as of and for the year ended December 31, 2013 included in the Company’s Annual Report on Form 10-K, which was filed with the SEC on February 18, 2014. The condensed balance sheet as of December 31, 2013, included herein, was derived from the audited financial statements as of that date.
	The unaudited condensed interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary to present fairly our financial position as of March 31, 2014, our results of operations for the three month periods ended March 31, 2014 and 2013, and our cash flows for the three months ended March 31, 2014 and 2013. The results of the three month period ended March 31, 2014 are not necessarily indicative of the results to be expected for the year ended December 31, 2014 or for any interim period or for any other future year.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make certain estimates, judgments and assumptions that affect the reported amounts of assets and liabilities and the related disclosures at the date of the financial statements, as well as the reported amounts of revenue and expenses during the periods presented. Estimates are used for revenue recognition, the allowance for doubtful accounts, website development costs, goodwill, recoverability of intangible assets with definite lives and other long-lived assets, and for share-based compensation. To the extent there are material differences between these estimates, judgments, or assumptions and actual results, our financial statements will be affected.
	Recently Issued Accounting Standards
	In July 2013, the Financial Accounting Standards Board (“FASB”) issued guidance on the presentation of certain unrecognized tax benefits in the financial statements. This guidance provides that a liability related to an unrecognized tax benefit must be offset against a deferred tax asset for a net operating loss carryforward, a similar tax loss or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. This guidance is effective for interim and annual reporting periods beginning after December 15, 2013, with earlier adoption permitted, and may be applied prospectively or retrospectively. We adopted this guidance on January 1, 2014. The adoption of this guidance did not have a significant impact on our financial position, results of operations or cash flows, as we have provided a full valuation allowance against our net deferred tax assets.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2014
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 — Cash equivalents are comprised of highly liquid investments, including money market funds, municipal securities and certificates of deposit, with original maturities of less than three months. The fair value measurement of these assets is based on observable market-based inputs or inputs that are derived principally from or corroborated by observable market data by correlation or other means.
	Short-term and long-term investments — Our investments consist of fixed income securities, which include U.S. government agency securities, corporate notes and bonds, municipal securities, certificates of deposit and commercial paper. Investments with maturities greater than three months but less than one year are classified as short-term investments. Investments with maturities greater than one year are classified as long-term investments. The fair value measurement of these assets is based on observable market-based inputs or inputs that are derived principally from or corroborated by observable market data by correlation or other means. Our short-term and long-term investments are classified as held-to-maturity and are recorded at amortized cost, as we do not intend to sell the investments, and it is not more likely than not that we will be required to sell these investments prior to maturity. The amortized cost of our short-term and long-term investments approximates their fair value.
	Of the short-term investments and long-term investments on hand as of March 31, 2014, 53% mature on or prior to March 31, 2015, and the remaining 47% mature on or prior to March 31, 2016.
	The following tables present the balances of assets measured at fair value on a recurring basis as of the dates presented (in thousands):
			March 31, 2014
			Total		Level 1		Level 2
	Cash equivalents:
	Money market funds		$	133,664	$	133,664	$	—
	Municipal securities			5,055		—		5,055
	Certificates of deposit			1,625		—		1,625
	Short-term investments:
	U.S government agency securities			99,978		99,978		—
	Corporate notes and bonds			23,942		—		23,942
	Municipal securities			15,173		—		15,173
	Certificates of deposit			11,682		—		11,682
	Commercial paper			4,985		—		4,985
	Long-term investments:
	U.S government agency securities			65,045		65,045		—
	Corporate notes and bonds			47,996		—		47,996
	Municipal securities			24,609		—		24,609
	Certificates of deposit			299		—		299
	Total		$	434,053	$	298,687	$	135,366
			December 31, 2013
			Total		Level 1		Level 2
	Cash equivalents:
	Money market funds		$	184,941	$	184,941	$	—
	U.S government agency securities			3,306		3,306		—
	Short-term investments:
	U.S government agency securities			78,448		78,448		—
	Commercial paper			3,998		—		3,998
	Corporate notes and bonds			11,085		—		11,085
	Long-term investments:
	U.S government agency securities			112,623		112,623		—
	Corporate notes and bonds			29,812		—		29,812
	Total		$	424,213	$	379,318	$	44,895
	We did not have any Level 3 assets or liabilities measured at fair value on a recurring basis as of March 31, 2014 or December 31, 2013.

Property_and_Equipment_Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2014
Property Plant And Equipment [Abstract]	'
Property and Equipment, Net	'
	Note 4.	Property and Equipment, net
	The following table presents the detail of property and equipment as of the dates presented (in thousands):
			March 31,			December 31,
			2014			2013
	Website development costs		$	52,547		$	50,408
	Computer equipment			9,670			8,238
	Leasehold improvements			8,435			7,320
	Software			2,297			1,807
	Construction-in-progress			5,183			3,289
	Office equipment, furniture and fixtures			4,317			3,661
	Property and equipment			82,449			74,723
	Less: accumulated amortization and depreciation			(51,335	)		(47,315	)
	Property and equipment, net		$	31,114		$	27,408
	We recorded amortization and depreciation expense related to property and equipment (other than website development costs) of $1.3 million and $0.6 million, respectively, during the three months ended March 31, 2014 and 2013.
	We capitalized $5.6 million and $3.9 million, respectively, in website development costs during the three months ended March 31, 2014 and 2013. Amortization expense for website development costs included in technology and development expenses was $4.2 million and $2.5 million, respectively, during the three months ended March 31, 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.

Intangible_Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2014
Goodwill And Intangible Assets Disclosure [Abstract]	'
Intangible Assets	'
	Note 5.	Intangible Assets
	The following tables present the detail of intangible assets subject to amortization as of the dates presented (in thousands):
			March 31, 2014
			Cost		Accumulated			Net
					Amortization
	Purchased content		$	14,115	$	(9,854	)	$	4,261
	Developed technology			18,835		(5,275	)		13,560
	Customer relationships			9,775		(2,314	)		7,461
	Trademarks			3,261		(803	)		2,458
	Total		$	45,986	$	(18,246	)	$	27,740
			December 31, 2013
			Cost		Accumulated			Net
					Amortization
	Purchased content		$	12,968	$	(8,846	)	$	4,122
	Developed technology			18,835		(4,417	)		14,418
	Customer relationships			9,775		(1,799	)		7,976
	Trademarks			3,261		(628	)		2,633
	Total		$	44,839	$	(15,690	)	$	29,149
	Amortization expense recorded for intangible assets for the three months ended March 31, 2014 and 2013 was $2.6 million and $1.7 million, respectively. These amounts are included in technology and development expenses.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Note 6.	Income Taxes
	We are subject to federal and state income taxes in the United States. During the three months ended March 31, 2014 and 2013, we did not have reportable taxable income, and we are not projecting reportable taxable income for the year ending December 31, 2014. We have provided a full valuation allowance against our net deferred tax assets as of March 31, 2014 and December 31, 2013 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. Therefore, no tax liability or expense has been recorded in the financial statements. We have accumulated federal tax losses of approximately $236.5 million as of December 31, 2013, which are available to reduce future taxable income. We have accumulated state tax losses of approximately $6.1 million (tax effected) as of December 31, 2013.

Shareholders_Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2014
Equity [Abstract]	'
Shareholders' Equity	'
	Note 7.	Shareholders’ Equity
	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 March 31, 2014 or December 31, 2013.
	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 upon the affirmative vote by or written consent of holders of a majority of the shares of the Class B common stock. During the three months ended March 31, 2014, 201,445 shares of Class B common stock were converted into Class A common stock at the option of the holders. During the year ended December 31, 2013, 993,634 shares 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.
	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. 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.

ShareBased_Awards

Share-Based Awards	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Share-Based Awards	'
	Note 8.	Share-Based Awards
	On July 19, 2011, our 2011 Incentive Plan (as amended and/or restated from time to time, the “2011 Plan”) became effective and replaced our 2005 Equity Incentive Plan. The 2011 Plan was subsequently amended and restated effective as of June 1, 2012, to, among other things, increase the total number of authorized shares and include the material terms of performance goals for performance-based awards. The 2011 Plan was further amended effective as of May 31, 2013 to increase the number of authorized shares of Class A common stock available for awards under the 2011 Plan by 1,500,000 shares such that a total of 3,800,000 shares of Class A common stock are available for issuance under the 2011 Plan. The 2011 Plan also contains an “evergreen” provision, pursuant to which the number of shares of Class A common stock available for issuance under the 2011 Plan can be increased on the first day of each of our fiscal years beginning in 2013 by a number of shares equal to the least of (a) 3.5% of our outstanding Class A common stock and Class B common stock on a fully diluted basis as of the end of our immediately preceding fiscal year, (b) 3,500,000 shares, 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. 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.
	Stock Options
	All stock options granted from inception through March 31, 2014 are nonqualified stock options, with the exception of substituted incentive stock options for 15,143 shares of Zillow’s Class A common stock that were granted in connection with the December 14, 2012 acquisition of HotPads, Inc. Options under the 2011 Plan are granted with an exercise price per share not less than 100% of the fair market value of our Class A common stock on the date of grant, with the exception of substituted stock options 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, except for options granted under the Stock Option Grant Program for Nonemployee Directors (“Nonemployee Director Awards”), which are fully vested and exercisable on the date of grant, and except for certain options that were granted to our chief executive officer in December 2012 and January 2013.
	The following table summarizes stock option activity for the year ended December 31, 2013 and the three months ended March 31, 2014:
			Shares			Number			Weighted-		Weighted-		Aggregate
			Available			of Shares			Average		Average		Intrinsic
			for Grant			Subject to			Exercise		Remaining		Value
						Existing			Price Per		Contractual
						Options			Share		Life (Years)
	Outstanding at January 1, 2013			321,678			5,462,672		$	14.48		4.48	$	78,912,364
	Authorized increase in plan shares			2,887,064			—			—
	Granted			(1,984,157	)		2,009,542			43.87
	Exercised			—			(2,026,829	)		9.03
	Forfeited or cancelled			288,679			(288,679	)		31.93
	Outstanding at December 31, 2013			1,513,264			5,156,706			27.09		5.43		283,008,505
	Authorized increase in plan shares			1,563,827			—			—
	Granted			(1,288,319	)		1,288,319			82.59
	Exercised			—			(309,750	)		16.99
	Forfeited or cancelled			60,423			(60,423	)		49.99
	Outstanding at March 31, 2014			1,849,195			6,074,852			39.15		5.57		298,096,008
	Vested and exercisable at March 31, 2014						1,798,723			16.03		4.05		129,635,359
	The shares available for grant identified in the above table exclude options for an aggregate of 25,385 shares, which options were granted in 2013 in substitution of options previously granted by StreetEasy, Inc. (“StreetEasy”). Pursuant to the terms of the 2011 Plan, such substituted stock option awards do not reduce the number of shares available for future issuance under the 2011 Plan. As of March 31, 2014, the numbers above do not include 87,270 shares of restricted stock and 86,832 restricted stock units outstanding under our 2011 Plan.
	The fair value of options granted, excluding Nonemployee Director Awards and certain options granted to the Company’s chief executive officer in December 2012 and January 2013, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model, assuming no dividends and with the following assumptions for the periods presented:
			Three Months Ended
			March 31,
			2014		2013
	Expected volatility		53%		51%
	Expected dividend yields		—		—
	Risk-free interest rate		1.37%		0.70%
	Weighted-average expected life		4.58 years		4.58 years
	Weighted-average fair value of options granted		$36.93		$16.28
	In the three months ended March 31, 2014, stock options for an aggregate of 23,010 shares of our Class A common stock were granted as Nonemployee Director Awards. The fair value of options granted for the Nonemployee Director Awards, $32.60 per share, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model, assuming no dividends, expected volatility of 54%, a risk-free interest rate of 0.69%, and a weighted-average expected life of 3.5 years. During the three months ended March 31, 2014 and 2013, share-based compensation expense recognized in our statement of operations related to Nonemployee Director Awards was $0.8 million and $0.5 million, respectively, and is included in general and administrative expenses.
	Restricted Stock Awards
	The following table summarizes restricted stock award activity for the year ended December 31, 2013 and the three months ended March 31, 2014:
			Shares of			Weighted-
			Restricted Stock			Average Grant-
						Date Fair
						Value
	Unvested outstanding at January 1, 2013			340,103		$	30.37
	Granted			3,673			44.66
	Vested			(108,379	)		30.94
	Forfeited or cancelled			(5,270	)		25.92
	Unvested outstanding at December 31, 2013			230,127			30.43
	Granted			3,255			80.91
	Vested			(19,026	)		40.18
	Forfeited or cancelled			—			—
	Unvested outstanding at March 31, 2014			214,356			30.33
	The fair value of the outstanding shares of restricted stock awards will be recorded as share-based compensation expense over the vesting period. As of March 31, 2014, there was $6.0 million of total unrecognized compensation cost related to restricted stock awards.
	Restricted Stock Units
	The following table summarizes activity for restricted stock units for the year ended December 31, 2013 and the three months ended March 31, 2014:
			Restricted Stock			Weighted-
			Units			Average Grant-
						Date Fair
						Value
	Unvested outstanding at January 1, 2013			295,737		$	38.76
	Granted			97,804			81.12
	Vested			(253,384	)		42.53
	Forfeited or cancelled			(19,034	)		59.26
	Unvested outstanding at December 31, 2013			121,123			64.07
	Granted			—			—
	Vested			(13,923	)		62.44
	Forfeited or cancelled			(20,368	)		75.42
Unvested outstanding at March 31, 2014			86,832			60.55
The fair value of restricted stock units will be recorded as share-based compensation expense over the vesting period. As of March 31, 2014, there was $5.2 million of total unrecognized compensation cost related to restricted stock units.
Share-Based Compensation Expense
The following table presents the effects of share-based compensation in our statements of operations during the periods presented (in thousands):
		Three Months Ended
		March 31,
		2014			2013
Cost of revenue		$	373		$	163
Sales and marketing			1,303			1,227
Technology and development			2,025			1,034
General and administrative			3,431			1,722
Total		$	7,132		$	4,146

Net_Loss_Per_Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Net Loss Per Share	'
	Note 9.	Net Loss Per Share
	Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares (including Class A common stock and Class B common 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 common shares (including Class A common stock and Class B common stock) outstanding during the period and potentially dilutive Class A common stock equivalents, except in cases where the effect of the Class A common stock equivalent would be antidilutive. Potential Class A common stock equivalents consist of Class A common stock issuable upon exercise of stock options and Class A common stock underlying unvested restricted stock awards and unvested restricted stock units using the treasury stock method.
	For the periods presented, the following Class A common stock equivalents were excluded from the calculations of diluted net loss per share because their effect would have been antidilutive (in thousands):
			Three Months Ended
			March 31,
			2014		2013
	Class A common stock issuable upon the exercise of stock options			2,959		2,856
	Class A common stock underlying unvested restricted stock awards and restricted stock units			97		130
	Total Class A common stock equivalents			3,056		2,986
	In the event of liquidation, dissolution, distribution of assets or winding-up of the Company, the holders of all classes of common stock have equal rights to receive all the assets of the Company after the rights of the holders of outstanding preferred stock have been satisfied. We have not presented net loss per share under the two-class method for our Class A common stock and Class B common 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	3 Months Ended
	Mar. 31, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Note 10.	Commitments and Contingencies
	Lease Commitments
	We have various operating leases for office space and equipment. In March 2011, we entered into a lease for approximately 66,000 square feet of office space that houses our corporate headquarters in Seattle, Washington, for which we are obligated to make escalating monthly lease payments that began in December 2012 and continue through November 2022. In June 2012, we entered into a lease amendment for our corporate headquarters in Seattle, Washington, which increased the rentable area of the premises by 21,575 square feet, for which we are obligated to make escalating monthly lease payments that began in January 2013 and continue through November 2022. In April 2013, we entered into a second lease amendment for our corporate headquarters in Seattle, Washington, which increased the rentable area of the premises by 22,583 square feet as of October 1, 2013, and will increase the rentable area of the premises by an additional 22,583 square feet as of September 1, 2014, for which we are obligated to make escalating monthly lease payments beginning in January 2014 and December 2014, respectively, and continuing through November 2022. In January 2014, we entered into a third lease amendment for our corporate headquarters in Seattle, Washington, to increase the rentable area of the premises by 22,694 square feet as of October 1, 2016, for which we are obligated to make escalating monthly lease payments beginning in January 2017 and continuing through November 2022. In April 2012, we entered into an operating lease in Irvine, California for 20,025 square feet under which we are obligated to make escalating monthly lease payments which began in August 2012 and continue through July 2022. In September 2013, we entered into a lease amendment for our operating lease in Irvine, California, which increased the rentable area of the premises by 20,024 square feet, for which we are obligated to make escalating monthly lease payments which began in February 2014 and continue through July 2022. 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 February 2014, we entered into an operating lease in New York, New York for 13,300 square feet under which we are obligated to make escalating monthly lease payments beginning in August 2014 and continuing through September 2024. We lease additional office space in Chicago, Illinois, Lincoln, Nebraska, and New York, New York.
	Future minimum payments for all operating leases as of March 31, 2014 are as follows (in thousands):
	Remainder of 2014			4,556
	2015			7,863
	2016			8,245
	2017			9,298
	2018			9,388
	All future years			33,496
	Total future minimum lease payments		$	72,846
	Rent expense for the three months ended March 31, 2014 and 2013 was $1.5 million and $1.1 million, respectively.
	Purchase Commitments
	As of March 31, 2014, we had non-cancelable purchase commitments for content related to our mobile applications and websites totaling $12.6 million. The amounts due for this content as of March 31, 2014 are as follows (in thousands):
	Remainder of 2014		$	3,503
	2015			4,650
	2016			3,599
	2017			817
	Total future purchase commitments		$	12,569
	Letters of Credit
	We have executed a standby letter of credit of $1.3 million in connection with the lease of our Seattle, Washington office space, and a standby letter of credit of $0.4 million in connection with the February 2014 lease of our New York, New York office. The letters of credit are secured by our investments and are effective until the expiration dates of the respective leases.
	Legal Proceedings
	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. 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, 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 August 26, 2013, we acquired StreetEasy, and took responsibility for the Smarter Agent complaint against StreetEasy. On December 14, 2012, we acquired HotPads, and took responsibility for the Smarter Agent complaint against HotPads. We have not recorded an accrual related to these complaints as of March 31, 2014 or December 31, 2013, as we do not believe a material loss is probable. It is a reasonable possibility that a loss may be incurred; however, the possible loss or range of loss is not estimable.
	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. On March 12, 2014, a federal jury found that Zillow does not infringe the patents and that the patents asserted by LendingTree are invalid. We have not recorded an accrual related to this complaint as of March 31, 2014 or December 31, 2013, as we do not believe a material loss is probable.
	In November 2012, a securities class action lawsuit was filed in the U.S. District Court for the Western District of Washington at Seattle against us and certain of our executive officers seeking unspecified damages. A consolidated amended complaint was filed in June 2013. The complaint purports to state claims for violations of federal securities laws on behalf of a class of those who purchased our common stock between February 15, 2012 and November 6, 2012. The complaint generally alleges, among other things, that during the period between February 15, 2012 and November 6, 2012, we issued materially false and misleading statements regarding our business practices and financial results. In August 2013, we moved to dismiss the lawsuit. That motion to dismiss has been fully briefed and is pending before the Court. We have denied the allegations of wrongdoing, and we will continue to vigorously defend the claims in the lawsuit. We have not recorded an accrual related to this lawsuit as of March 31, 2014 or December 31, 2013, as we do not believe a material loss is probable. It is a reasonable possibility that a loss may be incurred; however, the possible loss or range of loss is not 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 complaint seeks, among other things, an injunction against the alleged misappropriations and Mr. Samuelson working for us, as well as unspecified damages. In April 2014, the court denied the plaintiffs’ motion for a preliminary injunction prohibiting Mr. Samuelson from working for us. Plaintiffs renewed their motion for a preliminary injunction and that motion is pending. We have denied 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 March 31, 2014, as we do not believe a material loss is probable.
	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.

Segment_Information_and_Revenu

Segment Information and Revenue	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Segment Information and Revenue	'
	Note 11.	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):
			Three Months Ended
			March 31,
			2014		2013
	Marketplace revenue:
	Real estate		$	46,235	$	26,109
	Mortgages			7,128		4,909
	Total Marketplace revenue			53,363		31,018
	Display revenue			12,880		7,948
	Total revenue		$	66,243	$	38,966

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	Note 12.	Subsequent Events
	In April 2014, pursuant to the terms of an Amended and Restated Executive Employment Agreement and a Restricted Stock Unit Award Notice and Restricted Stock Unit Award Agreement entered into between Zillow and an employee, Zillow granted to the employee restricted stock units for 59,320 shares of our Class A common stock, which vest quarterly over four years beginning on the vesting commencement date of March 26, 2014, subject to the recipient’s continued full-time employment or service to Zillow. In the event of termination of service or employment by Zillow without cause or upon the resignation by such employee for good reason, the employee will receive 24 months’ accelerated vesting of the restricted stock units, except that in the event of such a termination in connection with a change in control, the restricted stock units will become fully vested. The employee will be entitled to receive one share of Zillow’s Class A common stock for each then outstanding unit that becomes vested. The grant date fair value of the restricted stock units is approximately $5.4 million and will be recorded as share-based compensation expense over the vesting period.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these interim condensed financial statements should be read in conjunction with the audited financial statements and accompanying notes as of and for the year ended December 31, 2013 included in the Company’s Annual Report on Form 10-K, which was filed with the SEC on February 18, 2014. The condensed balance sheet as of December 31, 2013, included herein, was derived from the audited financial statements as of that date.
	The unaudited condensed interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary to present fairly our financial position as of March 31, 2014, our results of operations for the three month periods ended March 31, 2014 and 2013, and our cash flows for the three months ended March 31, 2014 and 2013. The results of the three month period ended March 31, 2014 are not necessarily indicative of the results to be expected for the year ended December 31, 2014 or for any interim period or for any other future year.
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. Estimates are used for revenue recognition, the allowance for doubtful accounts, website development costs, goodwill, recoverability of intangible assets with definite lives and other long-lived assets, and for share-based compensation. To the extent there are material differences between these estimates, judgments, or assumptions and actual results, our financial statements will be affected.
Recently Issued Accounting Standards	'
	Recently Issued Accounting Standards
	In July 2013, the Financial Accounting Standards Board (“FASB”) issued guidance on the presentation of certain unrecognized tax benefits in the financial statements. This guidance provides that a liability related to an unrecognized tax benefit must be offset against a deferred tax asset for a net operating loss carryforward, a similar tax loss or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. This guidance is effective for interim and annual reporting periods beginning after December 15, 2013, with earlier adoption permitted, and may be applied prospectively or retrospectively. We adopted this guidance on January 1, 2014. The adoption of this guidance did not have a significant impact on our financial position, results of operations or cash flows, as we have provided a full valuation allowance against our net deferred tax assets.
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 — Cash equivalents are comprised of highly liquid investments, including money market funds, municipal securities and certificates of deposit, with original maturities of less than three months. The fair value measurement of these assets is based on observable market-based inputs or inputs that are derived principally from or corroborated by observable market data by correlation or other means.
	Short-term and long-term investments — Our investments consist of fixed income securities, which include U.S. government agency securities, corporate notes and bonds, municipal securities, certificates of deposit and commercial paper. Investments with maturities greater than three months but less than one year are classified as short-term investments. Investments with maturities greater than one year are classified as long-term investments. The fair value measurement of these assets is based on observable market-based inputs or inputs that are derived principally from or corroborated by observable market data by correlation or other means. Our short-term and long-term investments are classified as held-to-maturity and are recorded at amortized cost, as we do not intend to sell the investments, and it is not more likely than not that we will be required to sell these investments prior to maturity. The amortized cost of our short-term and long-term investments approximates their fair value.
Net Loss Per Share	'
	Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares (including Class A common stock and Class B common 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 common shares (including Class A common stock and Class B common stock) outstanding during the period and potentially dilutive Class A common stock equivalents, except in cases where the effect of the Class A common stock equivalent would be antidilutive. Potential Class A common stock equivalents consist of Class A common stock issuable upon exercise of stock options and Class A common stock underlying unvested restricted stock awards and unvested restricted stock units using the treasury stock 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.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements of Assets on Recurring Basis	'
	The following tables present the balances of assets measured at fair value on a recurring basis as of the dates presented (in thousands):
		March 31, 2014
		Total		Level 1		Level 2
	Cash equivalents:
	Money market funds	$	133,664	$	133,664	$	—
	Municipal securities		5,055		—		5,055
	Certificates of deposit		1,625		—		1,625
	Short-term investments:
	U.S government agency securities		99,978		99,978		—
	Corporate notes and bonds		23,942		—		23,942
	Municipal securities		15,173		—		15,173
	Certificates of deposit		11,682		—		11,682
	Commercial paper		4,985		—		4,985
	Long-term investments:
	U.S government agency securities		65,045		65,045		—
	Corporate notes and bonds		47,996		—		47,996
	Municipal securities		24,609		—		24,609
	Certificates of deposit		299		—		299
	Total	$	434,053	$	298,687	$	135,366
		December 31, 2013
		Total		Level 1		Level 2
	Cash equivalents:
	Money market funds	$	184,941	$	184,941	$	—
	U.S government agency securities		3,306		3,306		—
	Short-term investments:
	U.S government agency securities		78,448		78,448		—
	Commercial paper		3,998		—		3,998
	Corporate notes and bonds		11,085		—		11,085
	Long-term investments:
	U.S government agency securities		112,623		112,623		—
	Corporate notes and bonds		29,812		—		29,812
	Total	$	424,213	$	379,318	$	44,895

Property_and_Equipment_Net_Tab

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2014
Property Plant And Equipment [Abstract]	'
Details of Property and Equipment	'
	The following table presents the detail of property and equipment as of the dates presented (in thousands):
		March 31,			December 31,
		2014			2013
	Website development costs	$	52,547		$	50,408
	Computer equipment		9,670			8,238
	Leasehold improvements		8,435			7,320
	Software		2,297			1,807
	Construction-in-progress		5,183			3,289
	Office equipment, furniture and fixtures		4,317			3,661
	Property and equipment		82,449			74,723
	Less: accumulated amortization and depreciation		(51,335	)		(47,315	)
	Property and equipment, net	$	31,114		$	27,408

Intangible_Assets_Tables

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2014
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):
		March 31, 2014
		Cost		Accumulated			Net
				Amortization
	Purchased content	$	14,115	$	(9,854	)	$	4,261
	Developed technology		18,835		(5,275	)		13,560
	Customer relationships		9,775		(2,314	)		7,461
	Trademarks		3,261		(803	)		2,458
	Total	$	45,986	$	(18,246	)	$	27,740
		December 31, 2013
		Cost		Accumulated			Net
				Amortization
	Purchased content	$	12,968	$	(8,846	)	$	4,122
	Developed technology		18,835		(4,417	)		14,418
	Customer relationships		9,775		(1,799	)		7,976
	Trademarks		3,261		(628	)		2,633
	Total	$	44,839	$	(15,690	)	$	29,149

ShareBased_Awards_Tables

Share-Based Awards (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Summary of Stock Option Activity	'
	The following table summarizes stock option activity for the year ended December 31, 2013 and the three months ended March 31, 2014:
		Shares			Number			Weighted-		Weighted-		Aggregate
		Available			of Shares			Average		Average		Intrinsic
		for Grant			Subject to			Exercise		Remaining		Value
					Existing			Price Per		Contractual
					Options			Share		Life (Years)
	Outstanding at January 1, 2013		321,678			5,462,672		$	14.48		4.48	$	78,912,364
	Authorized increase in plan shares		2,887,064			—			—
	Granted		(1,984,157	)		2,009,542			43.87
	Exercised		—			(2,026,829	)		9.03
	Forfeited or cancelled		288,679			(288,679	)		31.93
	Outstanding at December 31, 2013		1,513,264			5,156,706			27.09		5.43		283,008,505
	Authorized increase in plan shares		1,563,827			—			—
	Granted		(1,288,319	)		1,288,319			82.59
	Exercised		—			(309,750	)		16.99
	Forfeited or cancelled		60,423			(60,423	)		49.99
	Outstanding at March 31, 2014		1,849,195			6,074,852			39.15		5.57		298,096,008
	Vested and exercisable at March 31, 2014					1,798,723			16.03		4.05		129,635,359
Fair Value of Options Granted, Excluding Non Employee Director Awards, Estimated at Date of Grant Using Black Scholes Merton Option Pricing Model	'
	The fair value of options granted, excluding Nonemployee Director Awards and certain options granted to the Company’s chief executive officer in December 2012 and January 2013, is estimated at the date of grant using the Black-Scholes-Merton option-pricing model, assuming no dividends and with the following assumptions for the periods presented:
		Three Months Ended
		March 31,
		2014		2013
	Expected volatility	53%		51%
	Expected dividend yields	—		—
	Risk-free interest rate	1.37%		0.70%
	Weighted-average expected life	4.58 years		4.58 years
	Weighted-average fair value of options granted	$36.93		$16.28
Summary of Restricted Stock Award Activity	'
	The following table summarizes restricted stock award activity for the year ended December 31, 2013 and the three months ended March 31, 2014:
		Shares of			Weighted-
		Restricted Stock			Average Grant-
					Date Fair
					Value
	Unvested outstanding at January 1, 2013		340,103		$	30.37
	Granted		3,673			44.66
	Vested		(108,379	)		30.94
	Forfeited or cancelled		(5,270	)		25.92
	Unvested outstanding at December 31, 2013		230,127			30.43
	Granted		3,255			80.91
	Vested		(19,026	)		40.18
	Forfeited or cancelled		—			—
	Unvested outstanding at March 31, 2014		214,356			30.33
Summary of Restricted Stock Units Activity	'
	The following table summarizes activity for restricted stock units for the year ended December 31, 2013 and the three months ended March 31, 2014:
		Restricted Stock			Weighted-
		Units			Average Grant-
					Date Fair
					Value
	Unvested outstanding at January 1, 2013		295,737		$	38.76
	Granted		97,804			81.12
	Vested		(253,384	)		42.53
	Forfeited or cancelled		(19,034	)		59.26
	Unvested outstanding at December 31, 2013		121,123			64.07
	Granted		—			—
	Vested		(13,923	)		62.44
	Forfeited or cancelled		(20,368	)		75.42
	Unvested outstanding at March 31, 2014		86,832			60.55
Effects of Share Based Compensation in Statements of Operations	'
	The following table presents the effects of share-based compensation in our statements of operations during the periods presented (in thousands):
		Three Months Ended
		March 31,
		2014			2013
	Cost of revenue	$	373		$	163
	Sales and marketing		1,303			1,227
	Technology and development		2,025			1,034
	General and administrative		3,431			1,722
	Total	$	7,132		$	4,146

Net_Loss_Per_Share_Tables

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Antidilutive Securities Excluded from Computation of Earnings Per Share	'
	For the periods presented, the following Class A common stock equivalents were excluded from the calculations of diluted net loss per share because their effect would have been antidilutive (in thousands):
		Three Months Ended
		March 31,
		2014		2013
	Class A common stock issuable upon the exercise of stock options		2,959		2,856
	Class A common stock underlying unvested restricted stock awards and restricted stock units		97		130
	Total Class A common stock equivalents		3,056		2,986

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Future Minimum Payments for All Operating Leases	'
	Future minimum payments for all operating leases as of March 31, 2014 are as follows (in thousands):
	Remainder of 2014		4,556
	2015		7,863
	2016		8,245
	2017		9,298
	2018		9,388
	All future years		33,496
	Total future minimum lease payments	$	72,846
Purchase Commitments for Content Related to Mobile Applications and Websites	'
	The amounts due for this content as of March 31, 2014 are as follows (in thousands):
	Remainder of 2014	$	3,503
	2015		4,650
	2016		3,599
	2017		817
	Total future purchase commitments	$	12,569

Segment_Information_and_Revenu1

Segment Information and Revenue (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Revenue Categories	'
	The following table presents our revenue categories during the periods presented (in thousands):
		Three Months Ended
		March 31,
		2014		2013
	Marketplace revenue:
	Real estate	$	46,235	$	26,109
	Mortgages		7,128		4,909
	Total Marketplace revenue		53,363		31,018
	Display revenue		12,880		7,948
	Total revenue	$	66,243	$	38,966

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
		Mature in 2015	Mature in 2016	Fair Value, Inputs, Level 3	Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Original maturities date of money market funds	'Less than three months	'	'	'	'
Investment classification	'Investments with maturities greater than three months but less than one year are classified as short-term investments. Investments with maturities greater than one year are classified as long-term investments.	'	'	'	'
Investment maturity, percentage	'	53.00%	47.00%	'	'
Investment maturity, year	'	'2015	'2016	'	'
Assets measured at fair value on recurring basis	'	'	'	$0	$0
Liabilities measured at fair value on recurring basis	'	'	'	$0	$0

Fair_Value_Measurement_of_Asse

Fair Value Measurement of Assets on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total	$434,053	$424,213
Money Market Funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	133,664	184,941
Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	5,055	'
Short-term investments	15,173	'
Long-term investments	24,609	'
Certificates of Deposit	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	1,625	'
Short-term investments	11,682	'
Long-term investments	299	'
U.S government agency securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	'	3,306
Short-term investments	99,978	78,448
Long-term investments	65,045	112,623
Commercial Paper	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	4,985	3,998
Corporate Notes and Bonds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	23,942	11,085
Long-term investments	47,996	29,812
Fair Value, Inputs, Level 1	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total	298,687	379,318
Fair Value, Inputs, Level 1 | Money Market Funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	133,664	184,941
Fair Value, Inputs, Level 1 | Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	'	'
Short-term investments	'	'
Long-term investments	'	'
Fair Value, Inputs, Level 1 | Certificates of Deposit	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	'	'
Short-term investments	'	'
Long-term investments	'	'
Fair Value, Inputs, Level 1 | U.S government agency securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	'	3,306
Short-term investments	99,978	78,448
Long-term investments	65,045	112,623
Fair Value, Inputs, Level 1 | Commercial Paper	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	'	'
Fair Value, Inputs, Level 1 | Corporate Notes and Bonds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	'	'
Long-term investments	'	'
Fair Value, Inputs, Level 2	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total	135,366	44,895
Fair Value, Inputs, Level 2 | Money Market Funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	'	'
Fair Value, Inputs, Level 2 | Municipal Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	5,055	'
Short-term investments	15,173	'
Long-term investments	24,609	'
Fair Value, Inputs, Level 2 | Certificates of Deposit	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	1,625	'
Short-term investments	11,682	'
Long-term investments	299	'
Fair Value, Inputs, Level 2 | U.S government agency securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	'	'
Short-term investments	'	'
Long-term investments	'	'
Fair Value, Inputs, Level 2 | Commercial Paper	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	4,985	3,998
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	23,942	11,085
Long-term investments	$47,996	$29,812

Detail_of_Property_and_Equipme

Detail of Property and Equipment (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	$82,449	$74,723
Less: accumulated amortization and depreciation	-51,335	-47,315
Property and equipment, net	31,114	27,408
Website development costs	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	52,547	50,408
Computer equipment	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	9,670	8,238
Leasehold improvements	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	8,435	7,320
Software	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	2,297	1,807
Construction-in-progress	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	5,183	3,289
Office equipment, furniture and fixtures	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment	$4,317	$3,661

Property_and_Equipment_Net_Add

Property and Equipment, Net - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Property, Plant and Equipment [Line Items]	'	'
Amortization and depreciation expense related to property and equipment other than website development costs	$1,300,000	$600,000
Capitalization of website development costs	5,600,000	3,900,000
Amortization of website development costs and intangible assets included in technology and development	6,784,000	4,208,000
Technology and Development	'	'
Property, Plant and Equipment [Line Items]	'	'
Amortization of website development costs and intangible assets included in technology and development	2,600,000	1,700,000
Technology and Development | Website development costs	'	'
Property, Plant and Equipment [Line Items]	'	'
Amortization of website development costs and intangible assets included in technology and development	$4,200,000	$2,500,000

Intangible_Assets_Detail

Intangible Assets (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'
Cost	$45,986	$44,839
Accumulated Amortization	-18,246	-15,690
Net	27,740	29,149
Purchased Content	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Cost	14,115	12,968
Accumulated Amortization	-9,854	-8,846
Net	4,261	4,122
Developed Technology	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Cost	18,835	18,835
Accumulated Amortization	-5,275	-4,417
Net	13,560	14,418
Customer Relationships	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Cost	9,775	9,775
Accumulated Amortization	-2,314	-1,799
Net	7,461	7,976
Trademarks	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Cost	3,261	3,261
Accumulated Amortization	-803	-628
Net	$2,458	$2,633

Intangible_Assets_Additional_I

Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Finite-Lived Intangible Assets [Line Items]	'	'
Amortization of website development costs and intangible assets included in technology and development	$6,784	$4,208
Technology and Development	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Amortization of website development costs and intangible assets included in technology and development	$2,600	$1,700

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Schedule Of Income Tax [Line Items]	'	'	'
Minimum estimated percentage of deferred tax unrealized	50.00%	'	'
Income tax liability	$0	'	$0
Income tax expense	0	0	'
Federal	'	'	'
Schedule Of Income Tax [Line Items]	'	'	'
Net operating loss carryforwards	'	'	236.5
State	'	'	'
Schedule Of Income Tax [Line Items]	'	'	'
Net operating loss carryforwards	'	'	$6.10

Shareholders_Equity_Additional

Shareholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Aug. 31, 2013	Mar. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]	'	'	'
Preferred stock, shares issued	'	0	0
Preferred stock, shares outstanding	'	0	0
Number of common stock converted	'	201,445	993,634
Net proceeds from issuance of common stock	$253.90	'	'
Class A Common Stock	'	'	'
Class of Stock [Line Items]	'	'	'
Common stock holders voting right	'	1	'
Conversion of common stock conversion ratio	'	1	'
Issuance of Class A common stock, shares	3,253,522	'	'
Class A Common Stock | Underwriters	'	'	'
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	$82	'	'
Class B Common Stock	'	'	'
Class of Stock [Line Items]	'	'	'
Common stock holders voting right	'	10	'

ShareBased_Awards_Additional_I

Share-Based Awards - Additional Information (Detail) (USD $)

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

31-May-13

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

HotPads, Inc.

StreetEasy, Inc.

Stock Options

Stock Options

Stock Options

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock Units

Restricted Stock Units

Restricted Stock Units

Non Employee Director

Non Employee Director

2011 Plan

2011 Plan

2011 Plan

2011 Plan

2011 Plan

2011 Plan

2011 Plan

Stock Options

Stock Options

Stock Options

Restricted Stock

Restricted Stock Units

Maximum

Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Increase in number of authorized shares available for awards

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,500,000

'

'

'

'

'

Total number of shares available for issuance under awards

'

'

'

'

1,849,195

1,513,264

321,678

'

'

'

'

'

'

'

'

'

3,800,000

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,500,000

'

'

'

'

'

'

Substituted incentive stock options granted in connection with acquisition

'

'

15,143

25,385

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercise price per share fixed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

Expiration period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'7 years

'10 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

'

'

'

'

Vesting percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

Vesting period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'36 months

'12 months

'

'

Number of shares outstanding

'

'

'

'

'

'

'

214,356

230,127

340,103

86,832

121,123

295,737

'

'

'

'

'

'

'

87,270

86,832

Stock option of Class A common stock granted

'

'

'

'

1,288,319

2,009,542

'

'

'

'

'

'

'

23,010

'

'

'

'

'

'

'

'

Fair value of options granted

$36.93

$16.28

'

'

'

'

'

'

'

'

'

'

'

$32.60

'

'

'

'

'

'

'

'

Expected volatility

53.00%

51.00%

'

'

'

'

'

'

'

'

'

'

'

54.00%

'

'

'

'

'

'

'

'

Risk-free interest rate

1.37%

0.70%

'

'

'

'

'

'

'

'

'

'

'

0.69%

'

'

'

'

'

'

'

'

Weighted-average expected life

'4 years 6 months 29 days

'4 years 6 months 29 days

'

'

'

'

'

'

'

'

'

'

'

'3 years 6 months

'

'

'

'

'

'

'

'

Recognized compensation cost

$7,132,000

$4,146,000

'

'

'

'

'

'

'

'

'

'

'

$800,000

$500,000

'

'

'

'

'

'

'

Total unrecognized compensation cost

'

'

'

'

'

'

'

$6,000,000

'

'

$5,200,000

'

'

'

'

'

'

'

'

'

'

'

Summary_of_Stock_Option_Activi

Summary of Stock Option Activity (Detail) (Stock Options, USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Shares Available for Grant, Beginning Balance	1,513,264	321,678	'
Shares Available for Grant, Authorized increase in plan shares	1,563,827	2,887,064	'
Shares Available for Grant, Granted	-1,288,319	-1,984,157	'
Shares Available for Grant, Exercised	'	'	'
Shares Available for Grant, Forfeited or cancelled	60,423	288,679	'
Shares Available for Grant, Ending Balance	1,849,195	1,513,264	321,678
Number of Shares Subject to Existing Options, Beginning Balance	5,156,706	5,462,672	'
Number of Shares Subject to Existing Options, Authorized increase in plan shares	'	'	'
Number of Shares Subject to Existing Options, Granted	1,288,319	2,009,542	'
Number of Shares Subject to Existing Options, Exercised	-309,750	-2,026,829	'
Number of Shares Subject to Existing Options, Forfeited or cancelled	-60,423	-288,679	'
Number of Shares Subject to Existing Options, Ending Balance	6,074,852	5,156,706	5,462,672
Weighted-Average Exercise Price Per Share, Beginning Balance	$27.09	$14.48	'
Number of Shares Subject to Existing Options, Vested and exercisable	1,798,723	'	'
Weighted-Average Exercise Price Per Share, Authorized increase in plan shares	'	'	'
Weighted-Average Exercise Price Per Share, Granted	$82.59	$43.87	'
Weighted-Average Exercise Price Per Share, Exercised	$16.99	$9.03	'
Weighted-Average Exercise Price Per Share, Forfeited or cancelled	$49.99	$31.93	'
Weighted-Average Exercise Price Per Share, Ending Balance	$39.15	$27.09	$14.48
Weighted-Average Exercise Price Per Share, Vested and exercisable	$16.03	'	'
Weighted-Average Remaining Contractual Life (Years)	'5 years 6 months 25 days	'5 years 5 months 5 days	'4 years 5 months 23 days
Weighted-Average Remaining Contractual Life (Years), Vested and exercisable	'4 years 18 days	'	'
Aggregate Intrinsic Value	$298,096,008	$283,008,505	$78,912,364
Aggregate Intrinsic Value Vested, and exercisable	$129,635,359	'	'

Fair_Value_of_Options_Granted_

Fair Value of Options Granted, Excluding Non Employee Director Awards, Estimated at Date of Grant Using Black Scholes Merton Option Pricing Model (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Expected volatility	53.00%	51.00%
Expected dividend yields	'	'
Risk-free interest rate	1.37%	0.70%
Weighted-average expected life	'4 years 6 months 29 days	'4 years 6 months 29 days
Weighted-average fair value of options granted	$36.93	$16.28

Summary_of_Restricted_Stock_Aw

Summary of Restricted Stock Award Activity (Detail) (Restricted Stock, USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Restricted Stock	'	'
Shares of Restricted Stock	'	'
Unvested outstanding, beginning balance	230,127	340,103
Granted	3,255	3,673
Vested	-19,026	-108,379
Forfeited or cancelled	'	-5,270
Unvested outstanding, ending balance	214,356	230,127
Weighted-Average Grant-Date Fair Value	'	'
Unvested outstanding, beginning balance	$30.43	$30.37
Granted	$80.91	$44.66
Vested	$40.18	$30.94
Forfeited or cancelled	'	$25.92
Unvested outstanding, ending balance	$30.33	$30.43

Summary_of_Restricted_Stock_Un

Summary of Restricted Stock Units Activity (Detail) (Restricted Stock Units, USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Restricted Stock Units	'	'
Restricted Stock Units	'	'
Unvested outstanding, beginning balance	121,123	295,737
Granted	'	97,804
Vested	-13,923	-253,384
Forfeited or cancelled	-20,368	-19,034
Unvested outstanding, ending balance	86,832	121,123
Weighted-Average Grant-Date Fair Value	'	'
Unvested outstanding, beginning balance	$64.07	$38.76
Granted	'	$81.12
Vested	$62.44	$42.53
Forfeited or cancelled	$75.42	$59.26
Unvested outstanding, ending balance	$60.55	$64.07

Effects_of_Share_Based_Compens

Effects of Share Based Compensation in Statements of Operations (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Share-based compensation	$7,132	$4,146
Cost of Revenue	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Share-based compensation	373	163
Sales and Marketing	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Share-based compensation	1,303	1,227
Technology and Development	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Share-based compensation	2,025	1,034
General and Administrative	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'
Share-based compensation	$3,431	$1,722

Antidilutive_Securities_Exclud

Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) (Class A Common Stock)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Class A common stock equivalents excluded from calculations of diluted net loss per share	3,056	2,986
Stock Options	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Class A common stock equivalents excluded from calculations of diluted net loss per share	2,959	2,856
Restricted Stock And Restricted Stock Units	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Class A common stock equivalents excluded from calculations of diluted net loss per share	97	130

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)

3 Months Ended

1 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Feb. 28, 2014

Sep. 30, 2010

Nov. 30, 2010

Mar. 31, 2010

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Feb. 28, 2014

Jan. 31, 2014

Sep. 30, 2013

Apr. 30, 2013

Nov. 30, 2012

Jun. 30, 2012

Apr. 30, 2012

Mar. 01, 2011

Patent

Smarter Agent

Smarter Agent

Smarter Agent

Smarter Agent

Smarter Agent

LendingTree, LLC

Operating Lease

Operating Lease

Operating Lease

Operating Lease

Operating Lease

Operating Lease

Operating Lease

Operating Lease

Patent

Patent

Diverse Solutions

StreetEasy, Inc.

HotPads, Inc.

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

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Rentable area of the premises

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13,300

22,694

20,024

22,583

18,353

21,575

20,025

66,000

Rent expense

$1,500,000

$1,100,000

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Non-cancelable purchase commitments for content

12,569,000

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Outstanding letters of credit

$1,300,000

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$400,000

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Number of patents-in-suit

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3

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Number of patents infringed

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2

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3

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Acquisition date

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31-Oct-11

26-Aug-13

14-Dec-12

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Allegations and asserted defenses

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'On March 12, 2014, a federal jury found that Zillow does not infringe the patents and that the patents asserted by LendingTree are invalid.

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Future_Minimum_Payments_for_Al

Future Minimum Payments for All Operating Leases (Detail) (USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
Remainder of 2014	$4,556
2015	7,863
2016	8,245
2017	9,298
2018	9,388
All future years	33,496
Total future minimum lease payments	$72,846

Purchase_Commitments_for_Conte

Purchase Commitments for Content Related to Mobile Applications and Websites (Detail) (USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
Remainder of 2014	$3,503
2015	4,650
2016	3,599
2017	817
Total future purchase commitments	$12,569

Segment_Information_and_Revenu2

Segment Information and Revenue - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2014
	Segment
Segment Reporting [Abstract]	'
Number of reportable segment	1

Revenue_Categories_Detail

Revenue Categories (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Revenues:	'	'
Total revenue	$66,243	$38,966
Marketplace revenue	'	'
Revenues:	'	'
Total revenue	53,363	31,018
Marketplace revenue | Real Estate Revenue	'	'
Revenues:	'	'
Total revenue	46,235	26,109
Marketplace revenue | Mortgages Revenue	'	'
Revenues:	'	'
Total revenue	7,128	4,909
Display revenue	'	'
Revenues:	'	'
Total revenue	$12,880	$7,948

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (Restricted Stock Units, USD $)	3 Months Ended	12 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Apr. 30, 2014
			Subsequent Events
Subsequent Event [Line Items]	'	'	'
Restricted stock units of Class A common stock granted	'	97,804	59,320
Restricted stock unit, award vesting period	'	'	'4 years
Vesting commencement date of restricted shares	26-Mar-14	'	'
Accelerated vesting period received by employee	'	'	'24 months
Terms of restricted stock unit award	'In the event of termination of service or employment by Zillow without cause or upon the resignation by such employee for good reason, the employee will receive 24 monthsb accelerated vesting of the restricted stock units, except that in the event of such a termination in connection with a change in control, the restricted stock units will become fully vested. The employee will be entitled to receive one share of Zillowbs Class A common stock for each then outstanding unit that becomes vested.	'	'
Fair value of restricted shares issued	'	'	$5.40