IAC InterActive (IAC) S-4/A 23 Feb 21 Registration of securities issued in business combination transactions (amended) Financial data

Cover Page

Cover Page	12 Months Ended
	Dec. 31, 2020
Document Information [Line Items]
Entity Central Index Key	0001800227
Amendment Flag	false
Document Type	S-4/A
Entity Registrant Name	IAC/INTERACTIVECORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	84-3727412
Entity Address, Address Line One	555 West 18th Street
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10011
City Area Code	212
Local Phone Number	314-7300
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Business Contact [Member]
Document Information [Line Items]
Contact Personnel Name	Kendall F. Handler, Esq.
Entity Address, Address Line One	555 West 18th Street
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10011
City Area Code	212
Local Phone Number	314-7300

CONSOLIDATED AND COMBINED BALAN

CONSOLIDATED AND COMBINED BALANCE SHEET - USD ($) shares in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash and cash equivalents	$ 3,476,188,000	$ 839,796,000
Marketable debt securities	224,979,000	0
Accounts receivable, net of allowance and reserves	270,453,000	181,875,000
Note receivable - related party	0	55,251,000
Other current assets	147,630,000	152,334,000
Total current assets	4,119,250,000	1,229,256,000
Building, capitalized software, leasehold improvements and equipment, net	278,251,000	305,414,000
Goodwill	1,879,438,000	1,616,867,000
Intangible assets, net of accumulated amortization	405,840,000	350,150,000
Long-term investments	297,643,000	347,975,000
Other non-current assets	294,860,000	247,746,000
TOTAL ASSETS	9,135,440,000	4,097,408,000
LIABILITIES:
Current portion of long-term debt	0	13,750,000
Accounts payable, trade	92,173,000	72,452,000
Deferred revenue	275,093,000	178,647,000
Accrued expenses and other current liabilities	383,562,000	320,473,000
Total current liabilities	750,828,000	585,322,000
Long-term debt, net	712,277,000	231,946,000
Income taxes payable	6,444,000	6,410,000
Deferred income taxes	52,593,000	44,459,000
Other long-term liabilities	230,378,000	180,307,000
Redeemable noncontrolling interests	231,992,000	43,818,000
Commitments and contingencies
SHAREHOLDERS' AND PARENT'S EQUITY:
Additional paid-in capital	5,909,614,000
Retained earnings	694,042,000	0
Invested capital		2,547,251,000
Accumulated Other Comprehensive Income (Loss), Net of Tax	(6,170,000)	(12,226,000)
Total IAC shareholders' and parent's equity, respectively	6,597,575,000	2,535,025,000
Noncontrolling interests	553,353,000	470,121,000
Total shareholders' and parent's equity, respectively	7,150,928,000	3,005,146,000
TOTAL LIABILITIES AND SHAREHOLDERS' AND PARENT'S EQUITY, RESPECTIVELY	9,135,440,000	4,097,408,000
MGM
ASSETS
Long-term investments	1,860,158,000	0
Common Stock
SHAREHOLDERS' AND PARENT'S EQUITY:
Common stock	$ 83,000	0
Common stock outstanding (shares)	82,976
Class B Common Stock
SHAREHOLDERS' AND PARENT'S EQUITY:
Common stock	$ 6,000	$ 0
Common stock outstanding (shares)	5,789

CONSOLIDATED AND COMBINED BAL_2

CONSOLIDATED AND COMBINED BALANCE SHEET (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Allowance and reserves of accounts receivable	$ 29,716	$ 24,148
Common Stock
Common stock, par value (USD per share)	$ 0.001
Common stock authorized (shares)	1,600,000,000
Common stock issued (shares)	82,976,000
Common stock outstanding (shares)	82,976,000
Class B Common Stock
Common stock, par value (USD per share)	$ 0.001
Common stock authorized (shares)	400,000,000
Common stock issued (shares)	5,789,000
Common stock outstanding (shares)	5,789,000

CONSOLIDATED AND COMBINED STATE

CONSOLIDATED AND COMBINED STATEMENT OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue	$ 3,047,681	$ 2,705,801	$ 2,533,048
Operating costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	814,731	600,240	501,152
Selling and marketing expense	1,269,673	1,202,183	1,099,487
General and administrative expense	792,254	617,235	569,802
Product development expense	267,359	193,457	177,298
Depreciation	69,283	55,949	42,393
Amortization of intangibles	141,584	83,868	107,081
Goodwill impairment	265,146	3,318	0
Total operating costs and expenses	3,620,030	2,756,250	2,497,213
Operating (loss) income	(572,349)	(50,449)	35,835
Interest expense	(16,166)	(11,904)	(13,059)
Unrealized gain on investment in MGM Resorts International	840,550	0	0
Other (expense) income, net	(42,468)	34,047	282,795
Earnings (loss) before income taxes	209,567	(28,306)	305,571
Income tax benefit (provision)	59,019	60,489	(13,200)
Net earnings	268,586	32,183	292,371
Net loss (earnings) attributable to noncontrolling interests	1,140	(9,288)	(45,599)
Net earnings attributable to IAC shareholders	$ 269,726	$ 22,895	$ 246,772
Per share information attributable to IAC shareholders:
Basic earnings per share (USD per share)	$ 3.16	$ 0.27	$ 2.90
Diluted earnings per share (USD per share)	$ 2.97	$ 0.27	$ 2.90
Stock-based compensation expense by function:
Total stock-based compensation expense	$ 197,220	$ 134,338	$ 148,405
Cost of revenue
Stock-based compensation expense by function:
Total stock-based compensation expense	191	74	195
Selling and marketing expense
Stock-based compensation expense by function:
Total stock-based compensation expense	5,869	5,185	4,345
General and administrative expense
Stock-based compensation expense by function:
Total stock-based compensation expense	182,068	118,709	132,180
Product development expense
Stock-based compensation expense by function:
Total stock-based compensation expense	$ 9,092	$ 10,370	$ 11,685

CONSOLIDATED AND COMBINED STA_2

CONSOLIDATED AND COMBINED STATEMENT OF COMPREHENSIVE OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net earnings	$ 268,586	$ 32,183	$ 292,371
Other comprehensive income (loss), net of income taxes:
Change in foreign currency translation adjustment	7,810	311	(6,444)
Change in unrealized gains and losses on available-for-sale marketable debt securities	2	(3)	3
Total other comprehensive income (loss), net of income taxes	7,812	308	(6,441)
Comprehensive income, net of income taxes	276,398	32,491	285,930
Components of comprehensive income attributable to noncontrolling interests:
Net loss (earnings) attributable to noncontrolling interests	1,140	(9,288)	(45,599)
Change in foreign currency translation adjustment attributable to noncontrolling interests	(1,718)	26	1,416
Change in unrealized gains and losses of available-for-sale marketable debt securities attributable to noncontrolling interests	0	1	(1)
Comprehensive income attributable to noncontrolling interests	(578)	(9,261)	(44,184)
Comprehensive income attributable to IAC shareholders	$ 275,820	$ 23,230	$ 241,746

CONSOLIDATED STATEMENT OF SHARE

CONSOLIDATED STATEMENT OF SHAREHOLDERS' AND COMBINED STATEMENT OF PARENT'S EQUITY - USD ($) shares in Thousands, $ in Thousands	Total IAC Shareholders' EquityCumulative Effect, Period of Adoption, Adjustment	Total IAC Shareholders' EquityOld IAC	Total IAC Shareholders' EquityVimeo	Total IAC Shareholders' Equity	Redeemable Noncontrolling InterestsVimeo	Redeemable Noncontrolling Interests	Common StockCommon Stock	Common StockClass B Common Stock	Additional Paid-in CapitalOld IAC	Additional Paid-in CapitalVimeo	Additional Paid-in Capital	Retained Earnings	Invested CapitalCumulative Effect, Period of Adoption, Adjustment	Invested Capital	Accumulated Other Comprehensive (Loss) Income	Noncontrolling InterestsCumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interests	Cumulative Effect, Period of Adoption, Adjustment	Old IAC	Vimeo	Total
Balance at beginning of period at Dec. 31, 2017						$ 36,811
Increase (Decrease) in Temporary Equity [Roll Forward]
Net earnings						33,788
Other comprehensive loss, net of income tax						(582)
Stock-based compensation expense						1,138
Distributions to and purchases of noncontrolling interests						(11,282)
Noncontrolling interests created in acquisitions						2,261
Adjustment of redeemable noncontrolling interests to fair value						6,640
Other						(3,087)
Balance at end of period at Dec. 31, 2018						65,687
Balance at beginning of period at Dec. 31, 2017	$ 36,927			$ 1,999,939									$ 36,927	$ 2,007,443	$ (7,504)	$ 3,410	$ 256,381	$ 40,337			$ 2,256,320
Increase (Decrease) in Shareholders' Equity
Net earnings				246,772										246,772			11,811				258,583
Other comprehensive loss, net of income tax				(5,026)											(5,026)		(833)				(5,859)
Stock-based compensation expense				51,327										51,327			95,940				147,267
Distributions to and purchases of noncontrolling interests																	(1,236)				(1,236)
Issuance of ANGI Homeservices common stock pursuant to stock-based awards, net of withholding taxes				106,204										106,215	(11)		34,502				140,706
Net increase in Old IAC's investment in IAC Holdings, Inc.				(145,461)										(145,461)							(145,461)
Adjustment of noncontrolling interests to fair value				(6,640)										(6,640)							(6,640)
Other				0										0			383				383
Balance at end of period at Dec. 31, 2018				2,284,042										2,296,583	(12,541)		400,358				2,684,400
Increase (Decrease) in Temporary Equity [Roll Forward]
Net earnings						3,168
Other comprehensive loss, net of income tax						39
Stock-based compensation expense						148
Distributions to and purchases of noncontrolling interests						(40,432)
Noncontrolling interests created in acquisitions						3,739
Adjustment of redeemable noncontrolling interests to fair value						11,554
Other						(85)
Balance at end of period at Dec. 31, 2019						43,818															43,818
Increase (Decrease) in Shareholders' Equity
Net earnings				22,895										22,895			6,120				29,015
Other comprehensive loss, net of income tax				335											335		(66)				269
Stock-based compensation expense				65,893										65,893			65,815				131,708
Issuance of ANGI Homeservices common stock pursuant to stock-based awards, net of withholding taxes				(32,616)										(32,596)	(20)		(2,106)				(34,722)
Purchase of ANGI Homeservices treasury stock				(57,949)										(57,949)							(57,949)
Net increase in Old IAC's investment in IAC Holdings, Inc.				263,979										263,979							263,979
Adjustment of noncontrolling interests to fair value				(11,554)										(11,554)							(11,554)
Other				0										0			0				0
Balance at end of period at Dec. 31, 2019				2,535,025			$ 0	$ 0			$ 0	$ 0		2,547,251	(12,226)		470,121				3,005,146
Balance at end of period (shares) at Dec. 31, 2019							0	0
Increase (Decrease) in Temporary Equity [Roll Forward]
Net earnings						(1,434)
Other comprehensive loss, net of income tax						439
Stock-based compensation expense						15
Distributions to and purchases of noncontrolling interests						(3,515)
Noncontrolling interests created in acquisitions						1,121
Issuance of Vimeo common stock and creation of noncontrolling interest, net of fees					$ 8,299
Adjustment of redeemable noncontrolling interests to fair value						183,315
Other						(66)
Balance at end of period at Dec. 31, 2020						$ 231,992															231,992
Increase (Decrease) in Shareholders' Equity
Net earnings				269,726								694,042		(424,316)			294				270,020
Other comprehensive loss, net of income tax				6,094											6,094		1,279				7,373
Stock-based compensation expense				113,761							40,870			72,891			85,267				199,028
Distributions to and purchases of noncontrolling interests																	(1,115)				(1,115)
Issuance of ANGI Homeservices common stock pursuant to stock-based awards, net of withholding taxes				(60,959)							(62,169)			1,248	(38)		(3,183)				(64,142)
Purchase of ANGI Homeservices treasury stock				(64,132)							(9,273)			(54,859)							(64,132)
Stock Issued During Period, Value, New Issues		$ 1,408,298							$ 1,408,298										$ 1,408,298
Net increase in Old IAC's investment in IAC Holdings, Inc.				1,685,995										1,685,995							1,685,995
Cash Merger Consideration Paid				837,913										837,913							837,913
Capitalization as a result of the MTCH Separation							$ 79	$ 6			4,661,231			(4,661,316)							0
Capitalization as a result of the Separation (shares)							79,343	5,789
Issuance of Vimeo common stock and creation of noncontrolling interest, net of fees			$ 141,301							$ 141,301										$ 141,301
Adjustment of noncontrolling interests to fair value				(183,315)							(178,508)			(4,807)							(183,315)
Issuance of common stock pursuant to stock-based awards, net of withholding taxes				(83,382)			$ 1				(83,383)										(83,382)
Issuance of common stock pursuant to stock-based awards, net of withholding taxes (shares)							633
Issuance of restricted stock							$ 3				(3)										0
Issuance of restricted stock (shares)							3,000
Adjustment to the capitalization of tax accounts as a result of the MTCH Separation				(8,259)							(8,259)										(8,259)
Other				(491)							(491)						690				199
Balance at end of period at Dec. 31, 2020				$ 6,597,575			$ 83	$ 6			$ 5,909,614	$ 694,042		$ 0	$ (6,170)		$ 553,353				$ 7,150,928
Balance at end of period (shares) at Dec. 31, 2020							82,976	5,789

CONSOLIDATED STATEMENT OF SHA_2

CONSOLIDATED STATEMENT OF SHAREHOLDERS' AND COMBINED STATEMENT OF PARENT'S EQUITY (Parenthetical)	Dec. 31, 2020$ / shares
Common Stock
Common stock, par value (USD per share)	$ 0.001
Class B Common Stock
Common stock, par value (USD per share)	0.001
Common Stock | Common Stock
Common stock, par value (USD per share)	0.001
Common Stock | Class B Common Stock
Common stock, par value (USD per share)	$ 0.001

CONSOLIDATED AND COMBINED STA_3

CONSOLIDATED AND COMBINED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net earnings	$ 268,586	$ 32,183	$ 292,371
Adjustments to reconcile net earnings to net cash provided by operating activities:
Stock-based compensation expense	197,220	134,338	148,405
Amortization of intangibles	141,584	83,868	107,081
Depreciation	69,283	55,949	42,393
Provision for credit losses	80,765	65,723	48,362
Goodwill impairment	265,146	3,318	0
Deferred income taxes	(31,920)	(62,770)	8,765
Unrealized gain on investment in MGM Resorts International	(840,550)	0	0
Losses (gains) on long-term investments in equity securities, net	40,824	(41,385)	(153,429)
(Gains) losses from the sale of businesses, net	(1,061)	8,239	(121,312)
Other adjustments, net	26,986	6,085	2,410
Changes in assets and liabilities, net of effects of acquisitions and dispositions:
Accounts receivable	(139,116)	(73,574)	(52,131)
Other assets	(4,002)	10,605	(29,802)
Accounts payable and other liabilities	11,566	889	35,611
Income taxes payable and receivable	(12,161)	196	4,302
Deferred revenue	81,431	28,136	36,409
Net cash provided by operating activities	154,581	251,800	369,435
Cash flows from investing activities:
Acquisitions, net of cash acquired	(684,618)	(196,578)	(65,632)
Capital expenditures	(61,570)	(97,898)	(54,680)
Proceeds from maturities of marketable debt securities	475,000	25,000	35,000
Purchases of marketable debt securities	(649,828)		(59,671)
Net proceeds from the sale of businesses and investments	26,343	164,828	136,311
Purchases of investments	(1,152)	(253,663)	(49,180)
Decrease (increase) in notes receivable - related party	54,828	(54,828)	0
Other, net	(11,536)	(8,729)	13,170
Net cash used in investing activities	(1,872,141)	(421,868)	(44,682)
Cash flows from financing activities:
Proceeds from issuance of related-party debt	0	0	2,500
Principal payments on related-party debt	0	(2,500)	0
Debt issuance costs	(6,484)	0	(3,709)
Distributions to and purchases of noncontrolling interests	(4,626)	(27,534)	(12,518)
Cash merger consideration paid by Old IAC in connection with the MTCH Separation	837,913	0	0
Transfers from Old IAC for periods prior to the MTCH Separation	1,706,479	263,281	(144,069)
Proceeds from the sale of Old IAC Class M common stock	1,408,298	0	0
Other, net	1,095	(3,795)	(1,041)
Net cash provided by (used in) financing activities	4,351,919	124,086	(197,738)
Total cash provided (used)	2,634,359	(45,982)	127,015
Effect of exchange rate changes on cash and cash equivalents and restricted cash	2,019	(122)	(118)
Net increase (decrease) in cash and cash equivalents and restricted cash	2,636,378	(46,104)	126,897
Cash and cash equivalents and restricted cash at beginning of period	840,732	886,836	759,939
MGM
Adjustments to reconcile net earnings to net cash provided by operating activities:
Unrealized gain on investment in MGM Resorts International	(840,500)
Cash flows from investing activities:
Purchases of investments	(1,019,608)	0	0
IAC/InterActiveCorp
Cash flows from financing activities:
Withholding taxes paid on behalf of employees on net settled stock-based awards	(85,103)	0	0
ANGI Homeservices
Cash flows from financing activities:
Proceeds from the issuance of ANGI Group Senior Notes	500,000	0	0
Principal payments on ANGI Group Term Loan	(27,500)	(13,750)	(13,750)
Purchase of ANGI Homeservices treasury stock	(63,674)	(56,905)	0
Proceeds from the exercise of ANGI Homeservices stock options	0	573	4,693
Withholding taxes paid on behalf of employees on net settled stock-based awards	(64,079)	(35,284)	(29,844)
Vimeo
Cash flows from financing activities:
Proceeds from issuance of Vimeo common stock, net of fees	$ 149,600	$ 0	$ 0

ORGANIZATION

ORGANIZATION	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	NOTE 1—ORGANIZATION MTCH Separation: On December 19, 2019, IAC/InterActiveCorp (“Old IAC”) entered into a Transaction Agreement (as amended as of April 28, 2020 and June 22, 2020, the “Transaction Agreement”) with Match Group, Inc. (“Old MTCH”), IAC Holdings, Inc. (“New IAC” or the “Company”), a direct wholly owned subsidiary of Old IAC, and Valentine Merger Sub LLC, an indirect wholly owned subsidiary of Old IAC. On June 30, 2020, the businesses of Old MTCH were separated from the remaining businesses of Old IAC through a series of transactions that resulted in the pre-transaction stockholders of Old IAC owning shares in two, separate public companies—(1) Old IAC, which was renamed Match Group, Inc. (“New Match”) and which owns the businesses of Old MTCH and certain Old IAC financing subsidiaries, and (2) New IAC, which was renamed IAC/InterActiveCorp, and which owns Old IAC’s other businesses—and the pre-transaction stockholders of Old MTCH (other than Old IAC) owning shares in New Match. This transaction is referred to as the “MTCH Separation”. Spin-off: On December 22, 2020, IAC announced that its Board of Directors approved a plan to spin-off its full stake in Vimeo to IAC shareholders. IAC’s Vimeo business will be separated from the remaining businesses of IAC through a series of transactions (which we refer to as the “Spin-off”) that, if completed in their entirety, will result in the transfer of IAC’s Vimeo business to Vimeo Holdings, Inc. (“SpinCo”), a newly formed subsidiary of IAC, with SpinCo becoming an independent, separately traded public company through a spin-off from IAC, and Vimeo, the IAC subsidiary that currently holds the Vimeo business, becoming a wholly-owned subsidiary of SpinCo. The proposed transaction is subject to a number of conditions including final approval by IAC’s Board of Directors, approval of the separation proposal by IAC stockholders, and other customary conditions and approvals and is expected to close in the second quarter of 2021. Company overview The Company operates Vimeo, Dotdash and Care.com, among many other online businesses, and has majority ownership of ANGI Homeservices, which operates HomeAdvisor, Angie’s List and Handy. ANGI Homeservices Our ANGI Homeservices segment includes the North American (United States and Canada) and European businesses and operations of ANGI Homeservices Inc. (“ANGI”). On September 29, 2017, the Company’s HomeAdvisor business and Angie’s List Inc. (“Angie’s List”) combined under a new publicly traded company called ANGI Homeservices Inc. (the “Combination”). At December 31, 2020, IAC’s economic interest and voting interest in ANGI were 84.3% and 98.2% , respectively. ANGI Homeservices Inc. connects quality home service professionals across 500 different categories, from repairing and remodeling to cleaning and landscaping, with consumers. Over 240,000 domestic service professionals actively sought consumer matches, completed jobs or advertised work through ANGI Homeservices’ platforms and consumers turn to at least one of our brands to find a professional for approximately 32 million projects during the year ended December 31, 2020. ANGI has established category-transforming products with brands such as HomeAdvisor, Angie’s List and Handy. ANGI’s Handy business is a leading platform in the United States for connecting individuals looking for household services (primarily cleaning and handyman services) with top-quality, pre-screened independent service professionals. ANGI also owns and operates mHelpDesk, a provider of cloud-based field service software for small to mid-size businesses. Prior to its sale on December 31, 2018, ANGI also operated Felix, a pay-per-call advertising service business. In addition to its market-leading U.S. operations, ANGI owns leading home services online marketplaces in France (Travaux), Germany (MyHammer), Netherlands (Werkspot), United Kingdom (MyBuilder Limited or “MyBuilder,” which we acquired a controlling interest in on March 24, 2017), Canada (HomeStars Inc. or “HomeStars,” which we acquired a controlling interest in on February 8, 2017) and Italy (Instapro), as well as operations in Austria (MyHammer). Vimeo Vimeo operates a cloud-based software platform for professionals, teams and organizations to create, collaborate and communicate with video. Vimeo’s all-in-one software solution makes video easier and more effective than ever before, offering the full range of video tools through a recurring software-as-a-service (“SaaS” model) that enables subscribers to create, stream, host, distribute, market, monetize and analyze videos online and across devices. At December 31, 2020, IAC held 89.7% of Vimeo’s Class A Voting common stock and 97.6% of Vimeo’s Class B Non-Voting common stock, or 93.2% of Vimeo’s total outstanding capital stock. Vimeo previously sold live streaming devices and accessories through its hardware business, prior to the sale of this business on March 29, 2019. Vimeo retained rights in the hardware business to participate in and receive distributions in the event of positive cash flows or proceeds from the sale of the business. On May 28, 2019, Vimeo purchased certain assets and assumed certain liabilities relating to the Magisto video creation app from Magisto, Ltd. (this transaction is referred herein to as the acquisition of Magisto). Dotdash Dotdash is a portfolio of digital publishing brands that collectively provide expert information and inspiration in select vertical content categories. Through our brands, Dotdash provides original and engaging digital content in a variety of formats, including articles, illustrations, videos and images. Search The Search segment consists of Ask Media Group and the Desktop business. Ask Media Group is a collection of websites providing general search services, and to a lesser extent, content that help users find the information they need. Through the Desktop business, we are a leading provider of global, advertising-driven desktop applications. We own and operate a portfolio of desktop browser applications that provide users with access to a wide variety of online content, tools and services. We provide users who download our desktop browser applications with new tab search services, as well as the option of default browser search services. We distribute our desktop browser applications to consumers free of charge on an opt-in basis directly through direct-to-consumer (primarily Chrome Web Store) and partnership distribution channels. Emerging & Other Our Emerging & Other segment primarily includes: ● Mosaic Group, a leading developer and provider of global subscription mobile applications. Mosaic Group has a portfolio of some of the largest and most popular applications including: o o o ● Care.com, the leading online destination for families to easily connect with caregivers for their children, aging parents, pets and homes and for a wide variety of caregivers to easily connect with families, which we acquired on February 11, 2020; ● Bluecrew, a technology driven staffing platform exclusively for flexible W-2 work, which we acquired a controlling interest in on February 26, 2018; ● The Daily Beast, a website dedicated to news, commentary, culture and entertainment that publishes original reporting and opinion from its roster of full-time journalists and contributors; ● NurseFly, a platform to efficiently connect healthcare professionals with job opportunities, which we acquired a controlling interest in on June 26, 2019; ● IAC Films, a provider of production and producer services for feature films, primarily for initial sale and distribution through theatrical releases and video-on-demand services in the United States and internationally; and ● For periods prior to their sales: o o o o

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 2—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Combination As used herein, “IAC,” “the Company,” “we,” “our” or “us” and similar terms refer to IAC/InterActiveCorp and its subsidiaries (unless the context requires otherwise). The Company prepares its consolidated and combined financial statements (collectively referred to herein as “financial statements”) in accordance with U.S. generally accepted accounting principles (“GAAP”). The Company’s financial statements were prepared on a consolidated basis beginning June 30, 2020 and on a combined basis for periods prior thereto. The difference in presentation is due to the fact that the final steps of the legal reorganization, including the contribution of all the entities that comprise the Company prior to the MTCH Separation, were not completed until June 30, 2020. The preparation of the financial statements on a combined basis for periods prior to June 30, 2020 allows for the financial statements to be presented on a consistent basis for all periods presented. The historical combined financial statements of the Company have been derived from the historical accounting records of Old IAC. The combined financial statements reflect the historical financial position, results of operations and cash flows of the entities comprising the Company since their respective dates of acquisition by Old IAC and the allocation to the Company of certain Old IAC corporate expenses based on the historical accounting records of Old IAC through June 30, 2020. The consolidated financial statements include the accounts of the Company, all entities that are wholly-owned by the Company and all entities in which the Company has a controlling financial interest. For the purpose of the combined financial statements, income taxes have been computed as if the entities comprising the Company filed tax returns on a standalone, separate basis for periods prior to the MTCH Separation. All intercompany transactions and balances between and among the Company and its subsidiaries have been eliminated. All intercompany transactions between (i) the Company and (ii) Old IAC and its subsidiaries for periods prior to the MTCH Separation are considered to be effectively settled for cash at the time the transaction was recorded. The total net effect of the settlement of these intercompany transactions is reflected in the statement of cash flows as a financing activity and in the balance sheet as “Invested capital.” In management’s opinion, the assumptions underlying the historical financial statements of the Company, including the basis on which the expenses have been allocated from Old IAC, are reasonable. However, the allocations may not reflect the expenses that the Company would have incurred as an independent, stand-alone company for the periods presented. COVID-19 Update and Impairments The impact on the Company from the COVID-19 outbreak, which has been declared a “pandemic” by the World Health Organization, has been varied. The extent to which developments related to the COVID-19 outbreak and measures designed to curb its spread continue to impact the Company’s business, financial condition and results of operations will depend on future developments, all of which are highly uncertain and many of which are beyond the Company’s control, including the speed of contagion, the development and implementation of effective preventative measures and possible treatments, the scope of governmental and other restrictions on travel, discretionary services and other activity, and public reactions to these developments. For example, these developments and measures have resulted in rapid and adverse changes to the operating environment in which we do business, as well as significant uncertainty concerning the near and long term economic ramifications of the COVID-19 outbreak, which have adversely impacted our ability to forecast our results and respond in a timely and effective manner to trends related to the COVID-19 outbreak. The longer the global outbreak and measures designed to curb the spread of the virus continue to adversely affect levels of consumer confidence, discretionary spending and the willingness of consumers to interact with other consumers, vendors and service providers face-to-face (and in turn, adversely affect demand for the Company’s various products and services), the greater the adverse impact is likely to be on the Company’s business, financial condition and results of operations and the more limited will be the Company’s ability to try and make up for delayed or lost revenues. When COVID-19 first impacted the Company’s ANGI Homeservices business in the spring of 2020, ANGI Homeservices experienced a decline in demand for service requests, driven primarily by decreases in demand in certain categories of jobs (particularly discretionary indoor projects). Toward the end of the spring of 2020, ANGI Homeservices experienced a rebound in service requests, exceeding pre-COVID-19 growth levels, driven by increased demand from homeowners who spent more time at home due to measures taken to reduce the spread of COVID-19. ANGI Homeservices continued to experience strong demand for home services in the second half of 2020. However, many service professionals’ businesses have been adversely impacted by labor and material constraints and many service professionals have limited capacity to take on new business, which has negatively impacted ANGI Homeservices’ ability to monetize this increased level of service requests. Vimeo has seen strong revenue growth as the demand for communication via video has increased due to the pandemic. The Search segment has experienced a decline in revenue due, in part, to the decrease in advertising rates due to the impact of COVID-19, which decrease in rates was more significant earlier in the year. In the quarter ended March 31, 2020, the Company determined that the effects of COVID-19 were an indicator of possible impairment for certain of its assets and identified the following impairments: ● a $ 212.0 million impairment related to the goodwill of the Desktop reporting unit; ● a $21.4 million impairment related to certain indefinite-lived intangible assets of the Desktop reporting unit; ● a $51.5 million impairment of certain equity securities without readily determinable fair values; and ● a $7.5 million impairment of a note receivable and a warrant related to certain investees. In the quarter ended September 30, 2020, the Company reassessed the fair values of the Desktop reporting unit and the related indefinite-lived intangible assets and recorded impairments equal to the remaining carrying value of the goodwill of $53.2 million and $10.8 million related to the intangible assets. The reduction in the Company’s fair value estimates of the Desktop business in the first and third quarters of 2020 was primarily due to lower consumer queries, increasing challenges in monetization and the reduced ability to market profitably due to browser policy changes implemented by Google and other browsers. The effects of COVID-19 on monetization were an additional factor. Refer to “Certain Risks and Concentrations—Services Agreement with Google” for additional information. There were no additional impairments identified during the year ended December 31, 2020. In addition, the United States, which represents 80% of the Company’s revenue for the year ended December 31, 2020, experienced a significant resurgence of the coronavirus and with record levels of COVID-19 infections being reported during the fourth quarter of 2020 and continuing into the first quarter of 2021. Europe, which is the second largest market for the Company’s products and services, has also seen a dramatic resurgence in COVID-19. This resurgence and the measures designed to curb its spread could materially and adversely affect our business, financial condition and results of operations. Accounting Estimates Management of the Company is required to make certain estimates, judgments and assumptions during the preparation of its financial statements in accordance with GAAP. These estimates, judgments and assumptions impact the reported amounts of assets, liabilities, revenue and expenses and the related disclosure of assets and liabilities. Actual results could differ from these estimates. On an ongoing basis, the Company evaluates its estimates, judgments and assumptions, including those related to: the fair values of cash equivalents and marketable debt and equity securities; the carrying value of accounts receivable, including the determination of the allowance for credit losses; the determination of revenue reserves; the determination of the customer relationship period for certain costs to obtain a contract with a customer; the carrying value of right-of-use assets (“ROU assets”); the useful lives and recoverability of building, capitalized software, leasehold improvements and equipment and definite-lived intangible assets; the recoverability of goodwill and indefinite-lived intangible assets; the fair value of equity securities without readily determinable fair values; contingencies; the fair value of acquisition-related contingent consideration arrangements; unrecognized tax benefits; the valuation allowance for deferred income tax assets; and the fair value of and forfeiture rates for stock-based awards, among others. The Company bases its estimates, judgments and assumptions on historical experience, its forecasts and budgets and other factors that the Company considers relevant. Accounting for Investments in Equity Securities Investments in equity securities, other than those of the Company’s consolidated subsidiaries and those accounted for under the equity method, if applicable, are accounted for at fair value or under the measurement alternative of Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , with any changes to fair value recognized within other (expense) income, net each reporting period. Under the measurement alternative, equity investments without readily determinable fair values are carried at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar securities of the same issuer; value is generally determined based on a market approach as of the transaction date. A security will be considered identical or similar if it has identical or similar rights to the equity securities held by the Company. The Company reviews its investments in equity securities without readily determinable fair values for impairment each reporting period when there are qualitative factors or events that indicate possible impairment. Factors the Company considers in making this determination include negative changes in industry and market conditions, financial performance, business prospects, and other relevant events and factors. When indicators of impairment exist, the Company prepares quantitative assessments of the fair value of its investments in equity securities, which require judgment and the use of estimates. When the Company’s assessment indicates that the fair value of the investment is below its carrying value, the Company writes down the investment to its fair value and records the corresponding charge within other (expense) income, net. See “Note 6 - Financial Instruments and Fair Value Measurements” for additional information on the impairments of certain equity securities without readily determinable fair values recorded during the year ended December 31, 2020. In the event the Company has investments in the common stock or in-substance common stock of entities in which the Company has the ability to exercise significant influence over the operating and financial matters of the investee, but does not have a controlling financial interest, are accounted for using the equity method and are included in “Long-term investments” in the accompanying balance sheet. At December 31, 2020, the Company has one investment accounted for using the equity method. At December 31, 2019, the Company did not have any investments accounted for using the equity method. Revenue Recognition The Company accounts for a contract with a customer when it has approval and commitment from all parties, the rights of the parties and payment terms are identified, the contract has commercial substance and collectability of consideration is probable. Revenue is recognized when control of the promised services or goods is transferred to our customers and in an amount that reflects the consideration the Company expects to be entitled to in exchange for those services or goods. The Company adopted ASU No. 2014-09, Revenue from Contracts with Customers, effective January 1, 2018 using the modified retrospective transition method for open contracts as of the date of initial application. The cumulative effect to the Company’s retained earnings at January 1, 2018 was an increase of $40.3 million, of which $3.4 million was related to the noncontrolling interest in ANGI; the adjustment to retained earnings was principally related to the Company’s ANGI segment and the Desktop business. ● Within ANGI, the effect of the adoption of ASU No. 2014-09 was that commissions paid to employees pursuant to certain sales incentive programs, which represent the incremental direct costs of obtaining a service professional contract, are now capitalized and amortized over the estimated life of a service professional (also referred to as the estimated customer relationship period). These costs were expensed as incurred prior to January 1, 2018. The cumulative effect of the adoption of ASU No. 2014-09 was the establishment of a current and non-current asset for capitalized sales commissions of $29.7 million and $4.2 million, respectively, and a related deferred tax liability of $ 8.0 million, resulting in a net increase to retained earnings of $25.9 million on January 1, 2018. ● Within the Desktop business, the primary effect of the adoption of ASU No. 2014-09 was to accelerate the recognition of the portion of the revenue of certain desktop applications sold by SlimWare that qualify as functional intellectual property (“functional IP”) under ASU No. 2014-09. This revenue was previously deferred and recognized over the applicable subscription term. The cumulative effect of the adoption of ASU No. 2014-09 for SlimWare was a reduction in deferred revenue of $20.3 million and the establishment of a deferred tax liability of $4.9 million, resulting in a net increase to retained earnings of $15.5 million on January 1, 2018. The Company’s disaggregated revenue disclosures are presented in “Note 12—Segment Information.” Transaction Price The objective of determining the transaction price is to estimate the amount of consideration the Company is due in exchange for its services or goods, including amounts that are variable. The Company determines the total transaction price, including an estimate of any variable consideration, at contract inception and reassesses this estimate each reporting period. The Company excludes from the measurement of transaction price all taxes assessed by governmental authorities that are both (i) imposed on and concurrent with a specific revenue-producing transaction and (ii) collected from customers. Accordingly, such tax amounts are not included as a component of revenue or cost of revenue. For contracts that have an original duration of one year or less, the Company uses the practical expedient available under ASU No. 2014-09, applicable to such contracts and does not consider the time value of money. Arrangements with Multiple Performance Obligations The Company’s contracts with customers may include multiple performance obligations. For such arrangements, the Company allocates revenue to each performance obligation based on its relative standalone selling price. The Company generally determines standalone selling prices based on the prices charged to customers, which are directly observable or based on an estimate if not directly observable. For our multiple performance obligation arrangements that include functional intellectual property (“IP”), which comprise the downloadable apps and software of the Desktop business, the Company uses a residual approach to determine standalone selling prices for the functional IP. Assets Recognized from the Costs to Obtain a Contract with a Customer The Company has determined that certain costs, primarily commissions paid to employees pursuant to certain sales incentive programs and mobile app store fees, meet the requirements to be capitalized as a cost of obtaining a contract. Commissions paid to employees pursuant to certain sales incentive programs are amortized over the estimated customer relationship period. The Company calculates the estimated customer relationship period as the average customer life, which is based on historical data. When customer renewals are expected and the renewal commission is not commensurate with the initial commission, the average customer life includes renewal periods. For sales incentive programs where the customer relationship period is one year or less, the Company has elected the practical expedient to expense the costs as incurred. The Company generally capitalizes and amortizes mobile app store fees over the term of the applicable subscription. During the years ended December 31, 2020, 2019 and 2018, the Company recognized expense of $109.0 million, $99.8 million and $70.6 million related to the amortization of these costs. The current contract asset balances are $61.5 million, $43.1 million and $40.6 million at December 31, 2020, 2019 and 2018, respectively. The non-current contract asset balances are $9.3 million, $6.2 million and $4.5 million at December 31, 2020, 2019 and 2018, respectively. The current and non-current contract assets are included in “Other current assets” and “Other non-current assets,” respectively, in the accompanying balance sheet. Performance Obligations As permitted under the practical expedient available under ASU No. 2014-09, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less, (ii) contracts with variable consideration that is allocated entirely to unsatisfied performance obligations or to a wholly unsatisfied promise accounted for under the series guidance, and (iii) contracts for which the Company recognizes revenue at the amount which it has the right to invoice for services performed. ANGI Homeservices ANGI revenue is primarily derived from consumer connection revenue, which comprises fees paid by HomeAdvisor service professionals for consumer matches (regardless of whether the service professional ultimately provides the requested service) and revenue from completed jobs sourced through the HomeAdvisor and Handy platforms. Consumer connection revenue varies based upon several factors, including the service requested, product experience offered and geographic location of service. The Company’s consumer connection revenue is generated and recognized when an in-network service professional is delivered a consumer match or when a job sourced through the HomeAdvisor and Handy platforms are completed. Consumer connection revenue is generally billed one week following a consumer match, with payment due upon receipt of invoice or collected when a consumer schedules a job through the HomeAdvisor and Handy platforms. The Company maintains revenue reserves for potential credits for services provided by Handy service professionals to consumers. ANGI revenue is also derived from (i) sales of time-based website, mobile and call center advertising to service professionals, (ii) HomeAdvisor service professional membership subscription fees, (iii) membership subscription fees from consumers and (iv) service warranty subscription and other services. Angie’s List service professionals generally pay for advertisements in advance on a monthly or annual basis at the option of the service professional, with the average advertising contract term being approximately one year . Angie’s List website, mobile and call center advertising revenue is recognized ratably over the contract term. Revenue from the sale of advertising in the Angie’s List Magazine is recognized in the period in which the publication is distributed. Service professional membership subscription revenue is initially deferred and is recognized using the straight-line method over the applicable subscription period, which is typically one year. Angie’s List prepaid consumer membership subscription fees are recognized as revenue using the straight-line method over the term of the applicable subscription period, which is typically one year. Prior to January 1, 2020, ANGI’s Handy business recorded revenue on a net basis. Effective January 1, 2020, ANGI modified the Handy terms and conditions so that Handy, rather than the service professional, has the contractual relationship with the consumer to deliver the service and Handy, rather than the consumer, has the contractual relationship with the service professional. Consumers request services and pay for such services directly through the Handy platform and then Handy fulfills the request with independently established home services providers engaged in a trade, occupation and/or business that customarily provides such services. This change in contractual terms requires gross revenue accounting treatment effective January 1, 2020. Also, in the case of certain tasks, HomeAdvisor provides a pre-priced product offering, pursuant to which consumers can request services through a HomeAdvisor platform and pay HomeAdvisor for the services directly. HomeAdvisor then fulfills the request with independently established home services providers engaged in a trade, occupation and/or business that customarily provides such services. Revenue from HomeAdvisor’s pre-priced product offering is also recorded on a gross basis effective January 1, 2020. The change to gross revenue reporting for Handy and HomeAdvisor’s pre-priced product offering, effective January 1, 2020, resulted in an increase in revenue of $73.8 million during the year ended December 31, 2020. Vimeo Vimeo revenue is derived primarily from annual and monthly SaaS subscription fees paid by subscribers for self-serve and enterprise subscription plans. Subscription revenue is recognized over the terms of the applicable subscription period, which range from one month to three years . The most common subscription is an annual subscription. Dotdash Dotdash revenue consists principally of display advertising revenue and performance marketing revenue. Display advertising revenue is generated primarily through digital display advertisements sold directly by our sales team and through programmatic advertising networks. Performance marketing revenue includes affiliate commerce and performance marketing commissions. Affiliate commerce commission revenue is generated when Dotdash refers users to commerce partner websites resulting in a purchase or transaction. Performance marketing commissions are generated on a cost-per-click or cost-per-action basis. Search Ask Media Group revenue consists principally of advertising revenue generated principally through the display of paid listings in response to search queries, as well as from display advertisements appearing alongside content on its various websites and, to a lesser extent, affiliate commerce commission revenue. Paid listings are advertisements displayed on search results pages that generally contain a link to advertiser websites. The majority of the paid listings displayed by Ask Media Group is supplied to us by Google Inc. (“Google”) pursuant to our services agreement with Google. Pursuant to this agreement, Ask Media Group businesses transmit search queries to Google, which in turn transmits a set of relevant and responsive paid listings back to these businesses for display in search results. This ad-serving process occurs independently of, but concurrently with, the generation of algorithmic search results for the same search queries. Google paid listings are displayed separately from algorithmic search results and are identified as sponsored listings on search results pages. Paid listings are priced on a price per click basis and when a user submits a search query through an Ask Media Group business and then clicks on a Google paid listing displayed in response to the query, Google bills the advertiser that purchased the paid listing and shares a portion of the fee charged to the advertiser with the Ask Media Group business. The Company recognizes paid listing revenue from Google when it delivers the user’s click. In cases where the user’s click is generated due to the efforts of a third-party distributor, we recognize the amount due from Google as revenue and record a revenue share or other payment obligation to the third-party distributor as traffic acquisition costs. Revenue from display advertising is generated through advertisements sold through programmatic advertising networks. Affiliate commerce commission revenue is generated when an Ask Media Group property refers users to commerce partner websites resulting in a purchase or transaction. Desktop revenue largely consists of advertising revenue generated principally through the display of paid listings in response to search queries. The majority of the paid listings displayed are supplied to us by Google in the manner, and pursuant to the services agreement with Google, described above. To a lesser extent, Desktop revenue also includes fees paid by subscribers for downloadable desktop applications as well as display advertisements. Fees related to subscription downloadable desktop applications are generally recognized over the term of the applicable subscription period, which is primarily one or two years . Fees related to display advertisements are recognized when an advertisement is displayed. Emerging & Other Mosaic Group revenue consists primarily of fees paid by subscribers for downloadable mobile applications distributed through the Apple App Store and Google Play Store and directly from consumers, as well as display advertisements. Fees related to subscription downloadable mobile applications are generally recognized either over the term of the subscription period, which is up to one year, for those applications that must be connected to our servers to function, or at the time of the sale when the software license is delivered. Fees related to display advertisements are recognized when an advertisement is displayed. Care.com generates revenue primarily through subscription fees from families and caregivers for its suite of products and services, as well as through annual contracts with corporate employers who provide access to Care.com’s suite of products and services as an employee benefit and through contracts with businesses that recruit employees through its platform. Bluecrew revenue consists of service revenue, which is generated through staffing workers and recognized as control of the promised services is transferred to our customers. The Daily Beast revenue consists of advertising revenue, which is generated primarily through display advertisements (sold directly and through programmatic ad sales), and to a lesser extent, affiliate commerce commission revenue. NurseFly revenue consists of subscription revenue, which is generated through recruiting agencies that seek access to qualified healthcare professionals and is recognized at the earlier of the full delivery of the promised services or the length of the subscription period. Revenue of IAC Films and College Humor Media, which was sold in the first quarter of 2020, is generated primarily through media production and distribution and advertising. Production revenue is recognized when control is transferred to the customer to broadcast or exhibit, and advertising revenue is recognized when an advertisement is displayed or over the advertising period. Accounts Receivables, Net of the Allowance for Credit Losses and Revenue Reserves Accounts receivable include amounts billed and currently due from customers. The allowance for credit losses is based upon a number of factors, including the length of time accounts receivable are past due, the Company’s previous loss history, the specific customer’s ability to pay its obligation and any other forward-looking data regarding customers’ ability to pay which may be available. The time between the Company issuance of an invoice and payment due date is not significant; customer payments that are not collected in advance of the transfer of promised services or goods are generally due no later than 30 days from invoice date. The Company also maintains allowances to reserve for potential credits issued to consumers or other revenue adjustments. The amounts of these reserves are based primarily upon historical experience. Credit Losses and Revenue Reserve The following table presents the changes in the allowance for credit losses for the year ended December 31, 2020: ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ (In thousands) Balance at January 1 ​ $ 20,257 Current period provision for credit losses ​ 80,765 Write-offs charged against the allowance ​ (75,815) Recoveries collected ​ 2,447 Balance at December 31 ​ $ 27,654 ​ The revenue reserve was $2.1 million and $3.9 million at December 31, 2020 and 2019, respectively. The total allowance for credit losses and revenue reserve was $29.7 million and $24.1 million as of December 31, 2020 and 2019, respectively. Deferred Revenue Deferred revenue consists of payments that are received or are contractually due in advance of the Company’s performance. The Company’s deferred revenue is reported on a contract by contract basis at the end of each reporting period. The Company classifies deferred revenue as current when the term of the applicable subscription period or expected completion of its performance obligation is one year or less. The current and non-current deferred revenue balances are $178.6 million and $1.3 million, respectively, at December 31, 2019 and $150.1 million and $1.7 million, respectively, at December 31, 2018. During the year ended December 31, 2019, the Company recognized $146.5 million of revenue that was included in the deferred revenue balance as of December 31, 2018. During the year ended December 31, 2020, the Company recognized $170.7 million of revenue that was included in the deferred revenue balance as of December 31, 2019. The current and non-current deferred revenue balances are $275.1 million and $1.5 million, respectively, at December 31, 2020. Non-current deferred revenue is included in “Other long-term liabilities” in the accompanying balance sheet. Cash and Cash Equivalents Cash and cash equivalents include cash and short-term investments, with maturities of less than 91 days from the date of purchase. Domestically, cash equivalents primarily consist of AAA rated government money market funds, treasury discount notes and time deposits. Internationally, cash equivalents primarily consist of AAA rated government money market funds and time deposits. Investments in Debt Securities The Company invests in marketable debt securities with active secondary or resale markets to ensure portfolio liquidity to fund current operations or satisfy other cash requirements as needed. Marketable debt securities are adjusted to fair value each quarter, and the unrealized gains and losses, net of tax, are included in accumulated other comprehensive income (loss) as a separate component of shareholders’ equity. The specific-identification method is used to determine the cost of debt securities sold and the amount of unrealized gains and losses reclassified out of accumulated other comprehensive income (loss) into earnings. The Company also invests in non-marketable debt securities as part of its investment strategy. We review our debt securities for impairment each reporting period. The Company recognizes an unrealized loss on debt securities in net earnings when the impairment is determined to be other-than-temporary. Factors we consider in making such determination include the duration, severity and reason for the decline in value and the potential recovery and our intent to sell the debt security. We also consider whether we will be required to sell the security before recovery of its amortized cost basis and whether the amortized co

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	NOTE 3—INCOME TAXES The Company was included within Old IAC’s tax group for purposes of federal and consolidated state income tax return filings through June 30, 2020, the date of the MTCH Separation. For periods prior thereto, the income tax benefit and/or provision were computed for the Company on an as if standalone, separate return basis and payments to and refunds from Old IAC for the Company’s share of Old IAC’s consolidated federal and state tax return liabilities/receivables calculated on this basis have been reflected within cash flows from operating activities in the accompanying statement of cash flows. U.S. and foreign earnings (loss) before income taxes and noncontrolling interests are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) U.S. ​ $ 197,545 ​ $ (74,360) ​ $ 269,267 Foreign ​ 12,022 ​ 46,054 ​ 36,304 Total ​ $ 209,567 ​ $ (28,306) ​ $ 305,571 ​ The components of the income tax (benefit) provision are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Current income tax (benefit) provision: ​ ​ ​ ​ ​ ​ Federal ​ $ (29,176) ​ $ (1,117) ​ $ (1,187) State ​ 2,253 ​ 197 ​ 1,514 Foreign ​ (176) ​ 3,201 ​ 4,108 Current income tax (benefit) provision ​ (27,099) ​ 2,281 ​ 4,435 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred income tax (benefit) provision: ​ ​ ​ Federal ​ (20,054) ​ (51,952) ​ 20,156 State ​ (7,726) ​ (10,645) ​ (7,272) Foreign ​ (4,140) ​ (173) ​ (4,119) Deferred income tax (benefit) provision ​ (31,920) ​ (62,770) ​ 8,765 Income tax (benefit) provision ​ $ (59,019) ​ $ (60,489) ​ $ 13,200 ​ The tax effects of cumulative temporary differences that give rise to significant deferred tax assets and deferred tax liabilities are presented below. The valuation allowance relates to deferred tax assets for which it is more likely than not that the tax benefit will not be realized. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Deferred tax assets: ​ ​ ​ Net operating loss carryforwards ​ $ 404,807 ​ $ 201,766 Stock-based compensation ​ 44,926 ​ 62,566 Long-term lease liabilities ​ 58,800 ​ 42,486 Tax credit carryforwards ​ 48,936 ​ 38,066 Accrued expenses ​ 20,490 ​ 12,911 Other ​ 34,024 ​ 21,039 Total deferred tax assets ​ 611,983 ​ 378,834 Less: valuation allowance ​ (113,684) ​ (92,990) Net deferred tax assets ​ 498,299 ​ 285,844 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ Investment in subsidiaries ​ (242,537) ​ (240,420) Investment in MGM Resorts International ​ (197,998) ​ — Right-of-use assets ​ (43,418) ​ (29,654) Intangible assets ​ (30,094) ​ (28,488) Other ​ (34,639) ​ (31,534) Total deferred tax liabilities ​ (548,686) ​ (330,096) Net deferred tax liabilities ​ $ (50,387) ​ $ (44,252) ​ As a result of the MTCH Separation, the Company’s net deferred tax liability was adjusted via invested capital for tax attributes allocated to it from Old IAC’s consolidated federal and state tax filings. The allocation of tax attributes that was recorded as of June 30, 2020 was preliminary. Any subsequent adjustment to allocated tax attributes will be recorded as an adjustment to deferred taxes and additional paid-in capital. This adjustment is expected to be made in the fourth quarter of 2021 following the filing of income tax returns for the year ended December 31, 2020. At December 31, 2020, the Company had federal and state net operating losses (“NOLs”) of $ 1.3 billion and $ 840.4 million, respectively, available to offset future income. Of these federal NOLs, $ 843.5 million can be carried forward indefinitely and $484.1 million, if not utilized, will expire at various times between 2024 and 2036. The state NOLs, if not utilized, will expire at various times between 2022 and 2040. Federal and state NOLs of $ 833.3 million and $ 543.8 million, respectively, can be used against future taxable income without restriction and the remaining NOLs will be subject to limitations under Section 382 of the IRC, separate return limitations, and applicable law. At December 31, 2020, the Company had foreign NOLs of $ 442.2 million available to offset future income. Of these foreign NOLs, $ 401.8 million can be carried forward indefinitely and $40.4 million, if not utilized, will expire at various times between 2021 and 2040. During 2020, the Company recognized tax benefits related to NOLs of $ 240.3 million. Included in this amount is $ 32.1 million of tax benefits of acquired attributes, which was recorded as a reduction to goodwill. At December 31, 2020, the Company had tax credit carryforwards of $ 66.2 million. Of this amount, $ 51.6 million relates to credits for research activities, $ 12.7 million relates to credits for foreign taxes, and $ 1.9 million relates to various other credits. Of these credit carryforwards, $ 11.5 million can be carried forward indefinitely and $ 54.7 million, if not utilized, will expire between 2021 and 2040. The Company regularly assesses the realizability of deferred tax assets considering all available evidence including, to the extent applicable, the nature, frequency and severity of prior cumulative losses, forecasts of future taxable income, tax filing status, the duration of statutory carryforward periods, available tax planning and historical experience. At December 31, 2020, the Company had a U.S. gross deferred tax asset of $ 489.8 million that the Company expects to fully utilize on a more likely than not basis. During 2020, the Company’s valuation allowance increased by $ 20.7 million primarily due to an increase in foreign NOLs and the impairments of certain equity securities without readily determinable fair values. At December 31, 2020, the Company had a valuation allowance of $ 113.7 million related to the portion of tax loss carryforwards, foreign tax credits and other items for which it is more likely than not that the tax benefit will not be realized. A reconciliation of the income tax (benefit)/provision to the amounts computed by applying the statutory federal income tax rate to earnings before income taxes is shown as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Income tax provision (benefit) at the federal statutory rate of 21% ​ $ 44,009 ​ $ (5,944) ​ $ 64,170 State income taxes, net of effect of federal tax benefit ​ 15,936 ​ (277) ​ 5,188 Stock-based compensation ​ (167,998) ​ (56,871) ​ (39,326) Non-deductible goodwill impairment ​ 53,012 ​ — ​ — Non-deductible executive compensation ​ 14,219 ​ 7,409 ​ 2,983 Change in valuation allowance on capital losses ​ 11,385 ​ (5,815) ​ (1,280) Research credit ​ (7,407) ​ (5,105) ​ (3,167) Amortizable tax basis related to intercompany transaction ​ (7,044) ​ — ​ — Non-deductible expenses ​ 6,556 ​ 5,460 ​ 1,727 Change in judgement on beginning of the year valuation allowance ​ (3,544) ​ — ​ — Net adjustment related to the reconciliation of income tax provision accruals to tax returns ​ (2,591) ​ 138 ​ 42 Deferred tax adjustment for enacted changes in tax laws and rates ​ (14,579) ​ (687) ​ (13,646) Other, net ​ (973) ​ 1,203 ​ (3,491) Income tax (benefit) provision ​ $ (59,019) ​ $ (60,489) ​ $ 13,200 ​ A reconciliation of the beginning and ending amount of unrecognized tax benefits, including penalties but excluding interest, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Balance at January 1 ​ $ 18,060 ​ $ 15,451 ​ $ 14,528 Additions based on tax positions related to the current year ​ 3,977 ​ 2,781 ​ 1,455 Settlements ​ (4,309) ​ — ​ — Additions for tax positions of prior years ​ 2,781 ​ 238 ​ 235 Expiration of applicable statutes of limitations ​ ​ (351) ​ ​ (410) ​ ​ (767) Balance at December 31 ​ $ 20,158 ​ $ 18,060 ​ $ 15,451 ​ The Company is routinely under audit by federal, state, local and foreign authorities in the area of income tax as a result of previously filed separate company and consolidated tax returns with Old IAC and will be under audit for its tax returns filed on a standalone basis following the MTCH Separation. These audits include questioning the timing and the amount of income and deductions and the allocation of income and deductions among various tax jurisdictions. The Internal Revenue Service (“IRS”) has substantially completed its audit of Old IAC’s federal income tax returns for the years ended December 31, 2010 through 2016, which includes the operations of the Company. The IRS began its audit of the year ended December 31, 2017 in the second quarter of 2020. The statute of limitations for the years 2010 through 2012 and for the years 2013 through 2017 have been extended to May 31, 2021 and December 31, 2021, respectively. Returns filed in various other jurisdictions are open to examination for tax years beginning with 2009. Income taxes payable include unrecognized tax benefits considered sufficient to pay assessments that may result from the examination of prior year tax returns. The Company considers many factors when evaluating and estimating its tax positions and tax benefits, which may not accurately anticipate actual outcomes and, therefore, may require periodic adjustment. Although management currently believes changes in unrecognized tax benefits from period to period and differences between amounts paid, if any, upon resolution of issues raised in audits and amounts previously provided will not have a material impact on the liquidity, results of operations, or financial condition of the Company, these matters are subject to inherent uncertainties and management’s view of these matters may change in the future. The Company recognizes interest and, if applicable, penalties related to unrecognized tax benefits in the income tax provision. At December 31, 2020 and 2019, accruals for interest and penalties are not material. At December 31, 2020 and 2019, unrecognized tax benefits, including interest and penalties, were $ 22.1 million and $ 20.3 million, respectively. Included in unrecognized tax benefits at December 31, 2019 is $ 11.6 million for tax positions included in Old IAC’s consolidated tax return filings. If unrecognized tax benefits at December 31, 2020 are subsequently recognized, $ 20.4 million, net of related deferred tax assets and interest, would reduce income tax expense. The comparable amount as of December 31, 2019 was $ 18.9 million. The Company believes that it is reasonably possible that its unrecognized tax benefits could decrease by $ 6.1 million by December 31, 2021, due to expirations of statutes of limitations or other settlements; all of which would reduce the income tax provision. At December 31, 2020, all of the Company’s international cash can be repatriated without any significant tax consequences. ​

BUSINESS COMBINATION

BUSINESS COMBINATION	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
BUSINESS COMBINATION	NOTE 4—BUSINESS COMBINATION On February 11, 2020, the Company acquired 100% of Care.com, a leading global platform for finding and managing family care, for a total purchase price of $ 626.9 million, which includes cash consideration of $ 587.0 million paid by the Company and the settlement of all outstanding vested employee equity awards for $ 40.0 million paid by Care.com prior to the completion of the acquisition. The Company’s purchase accounting is not yet complete and will be finalized in the first quarter of 2021; the determination of the fair value of certain contingent liabilities and acquired tax attributes is preliminary and subject to revision. During the fourth quarter of 2020, the Company completed a preliminary assessment of net operating losses acquired. As a result, the Company revised the purchase price allocation by increasing the fair value of deferred tax assets by $ 32.1 million and decreasing goodwill by $ 32.1 million. The table below summarizes the preliminary estimated fair values of the assets acquired and liabilities assumed at the date of acquisition: ​ ​ ​ ​ ​ ​ Care.com ​ ​ (In thousands) Cash and cash equivalents ​ $ 57,702 Short-term investments ​ 20,000 Accounts receivable ​ 20,213 Other current assets ​ 7,479 Property and equipment ​ 2,894 Goodwill ​ 404,313 Intangible assets ​ 116,800 Deferred income taxes ​ 32,112 Other non-current assets ​ 30,444 Total assets ​ 691,957 Deferred revenue ​ (13,422) Other current liabilities ​ (39,698) Deferred income taxes ​ (25,824) Other non-current liabilities ​ (26,039) Net assets acquired ​ $ 586,974 ​ The Company acquired Care.com because it is complementary to other marketplace businesses of IAC. The purchase price was based on the expected financial performance of Care.com, not on the value of the net identifiable assets at the time of acquisition. This resulted in a significant portion of the purchase price being attributed to goodwill. The fair values of the identifiable intangible assets acquired at the date of acquisition are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Care.com ​ ​ ​ Useful Life ​ ​ (In thousands) ​ (Years) Indefinite-lived trade name and trademarks ​ $ 59,300 Indefinite Developed technology ​ 21,200 2 Customer relationships ​ 35,500 2 - 5 Provider relationships ​ 800 4 Total identifiable intangible assets acquired ​ $ 116,800 ​ ​ Accounts receivable, other current assets, other non-current assets, other current liabilities and other non-current liabilities of Care.com were reviewed and adjusted to their fair values at the date of acquisition, as necessary. The fair value of deferred revenue was determined using an income approach that utilized a cost to fulfill analysis. The fair values of the trade name and developed technology were determined using an income approach that utilized the relief from royalty methodology. The fair values of customer relationships and provider relationships were determined using an income approach that utilized the excess earnings methodology. The valuations of the intangible assets incorporate significant unobservable inputs and require significant judgment and estimates, including the amount and timing of future cash flows and the determination of royalty and discount rates. The amount attributed to goodwill is not tax deductible. The financial results of Care.com are included in the Company’s financial statements, within the Emerging & Other segment, beginning February 11, 2020. For the year ended December 31, 2020, the Company included $ 182.4 million of revenue and $ 31.4 million of net loss in its statement of operations related to Care.com. For the year ended December 31, 2020, the net loss of Care.com reflects a reduction in revenue of $ 17.3 million due to the write-off of deferred revenue due to purchase accounting fair value adjustments and $ 16.7 million in transaction-related costs, including severance. Unaudited pro forma financial information The unaudited pro forma financial information in the table below presents the results of the Company and Care.com as if this acquisition had occurred on January 1, 2019. The unaudited pro forma financial information includes adjustments required under the acquisition method of accounting and is presented for informational purposes only and is not necessarily indicative of the results that would have been achieved had the acquisition occurred on January 1, 2019. For the year ended December 31, 2020, pro forma adjustments include a reduction in transaction related costs (including stock-based compensation expense related to the acceleration of vesting of outstanding employee equity awards) of $ 72.8 million because they are one-time in nature and will not have a continuing impact on operations and an increase in revenue of $ 17.1 million related to deferred revenue written off as a part of the acquisition. For the year ended December 31, 2019, pro forma adjustments include an increase in amortization of intangibles of $ 25.9 million and a decrease in revenue of $ 11.1 million related to the deferred revenue written off as a part of the acquisition. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 ​ ​ (In thousands, except per share data) Revenue ​ $ 3,090,779 ​ $ 2,904,243 Net earnings (loss) attributable to IAC shareholders ​ $ 296,933 ​ $ (16,926) Basic earnings (loss) per share attributable to IAC shareholders ​ $ 3.48 ​ $ (0.20) Diluted earnings (loss) per share attributable to IAC shareholders ​ $ 3.26 ​ $ (0.20) ​

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	​ NOTE 5—GOODWILL AND INTANGIBLE ASSETS Goodwill and intangible assets, net are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Goodwill ​ $ 1,879,438 ​ $ 1,616,867 Intangible assets with indefinite lives ​ 246,913 ​ 225,296 Intangible assets with definite lives, net of accumulated amortization ​ 158,927 ​ 124,854 Total goodwill and intangible assets, net ​ $ 2,285,278 ​ $ 1,967,017 ​ The following table presents the balance of goodwill by reportable segment, including the changes in the carrying value of goodwill, for the year ended December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Balance at ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ December 31, ​ 2019 Additions (Deductions) Impairment Translation 2020 ​ ​ (In thousands) ANGI Homeservices ​ $ 884,296 ​ $ 2,665 ​ $ — ​ $ — ​ $ 5,172 ​ $ 892,133 Vimeo ​ 219,374 ​ — ​ (38) ​ — ​ — ​ 219,336 Search ​ 265,146 ​ — ​ — ​ (265,146) ​ — ​ — Emerging & Other ​ 248,051 ​ 519,405 ​ — ​ — ​ 513 ​ 767,969 Total ​ $ 1,616,867 ​ $ 522,070 ​ $ (38) ​ $ (265,146) ​ $ 5,685 ​ $ 1,879,438 ​ Additions are primarily related to the acquisitions of Care.com (included in the Emerging & Other segment) and LifeCare (acquired by Care.com in October 2020). In the quarter ended March 31, 2020, the Company determined that the effects of COVID-19 were an indicator of possible impairment for certain of its reporting units and indefinite-lived intangible assets and identified a $ 212.0 million impairment related to the goodwill of the Desktop reporting unit and a $ 21.4 million impairment related to certain indefinite-lived intangible assets of the Desktop reporting unit. In the quarter ended September 30, 2020, the Company reassessed the fair values of the Desktop reporting unit and the related indefinite-lived intangible assets and recorded impairments equal to the remaining carrying value of the goodwill of $ 53.2 million and $ 10.8 million related to the intangible assets. The reduction in the Company’s fair value estimates of the Desktop business in the first and third quarters of 2020 was primarily due to lower consumer queries, increasing challenges in monetization and the reduced ability to market profitably due to policy changes implemented by Google and other browsers. The effects of COVID-19 on monetization were an additional factor. See “Note 2—Summary of Significant Accounting Policies” for further discussion of the Company’s assessments of impairment of goodwill and indefinite-lived intangible assets. The following table presents the balance of goodwill by reportable segment, including the changes in the carrying value of goodwill, for the year ended December 31, 2019 : ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Balance at ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ December 31, ​ 2018 Additions (Deductions) Impairment Translation 2019 ​ ​ (In thousands) ANGI Homeservices ​ $ 895,071 ​ $ 18,326 ​ $ (29,293) ​ $ — ​ $ 192 ​ $ 884,296 Vimeo ​ 77,152 ​ 142,222 ​ — ​ — ​ — ​ 219,374 Search ​ 265,146 ​ — ​ — ​ — ​ — ​ 265,146 Emerging & Other ​ 246,748 ​ 4,765 ​ — ​ (3,318) ​ (144) ​ 248,051 Total ​ $ 1,484,117 ​ $ 165,313 ​ $ (29,293) ​ $ (3,318) ​ $ 48 ​ $ 1,616,867 ​ Additions primarily relate to the acquisitions of Magisto (included in the Vimeo segment) and Fixd Repair (included in the ANGI Homeservices segment). Deductions primarily relate to tax benefits of acquired attributes related to the acquisition of Handy (included in the ANGI Homeservices segment). During the fourth quarter of 2019, the Company recorded an impairment of $3.3 million related to the goodwill of the College Humor Media business (included in the Emerging & Other Segment), which was sold on March 16, 2020. The December 31, 2020 goodwill balances reflect accumulated impairment losses of $ 981.3 million and $ 198.3 million at Search and Dotdash, respectively. The December 31, 2019 goodwill balances reflect accumulated impairment losses of $ 716.2 million and $ 198.3 million at Search and Dotdash, respectively, and $ 14.9 million related to College Humor Media (included in the Emerging & Other segment). As a result of the impairments that were recorded prior to January 1, 2019, the Dotdash reportable segment has no goodwill. At December 31, 2020 and 2019, intangible assets with definite lives are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ Gross ​ ​ ​ ​ ​ ​ ​ Average ​ ​ Carrying ​ Accumulated ​ ​ ​ ​ Useful Life ​ Amount Amortization Net (Years) ​ ​ (In thousands) ​ ​ Technology ​ $ 167,997 ​ $ (102,355) ​ $ 65,642 4.1 Service professional relationships ​ 97,960 ​ (97,312) ​ 648 3.0 Customer lists and user base ​ 91,887 ​ (33,864) ​ 58,023 4.0 Trade names ​ 53,383 ​ (19,227) ​ 34,156 6.6 Memberships ​ 15,900 ​ (15,900) ​ — 3.0 Other ​ 10,439 ​ (9,981) ​ 458 3.4 Total ​ $ 437,566 ​ $ (278,639) ​ $ 158,927 4.1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ Gross ​ ​ ​ ​ ​ ​ ​ Average ​ ​ Carrying ​ Accumulated ​ ​ ​ ​ Useful Life ​ Amount Amortization Net (Years) ​ ​ (In thousands) ​ ​ Technology ​ $ 143,255 ​ $ (73,483) ​ $ 69,772 4.5 Service professional relationships ​ 99,651 ​ (76,445) ​ 23,206 2.9 Customer lists and user base ​ 44,286 ​ (24,226) ​ 20,060 3.3 Trade names ​ 12,777 ​ (8,082) ​ 4,695 3.5 Memberships ​ 15,900 ​ (11,940) ​ 3,960 3.0 Other ​ 10,439 ​ (7,278) ​ 3,161 3.4 Total ​ $ 326,308 ​ $ (201,454) ​ $ 124,854 3.7 ​ At December 31, 2020, amortization of intangible assets with definite lives for each of the next five years and thereafter is estimated to be as follows: ​ ​ ​ ​ ​ Years Ending December 31, (In thousands) 2021 ​ $ 62,600 2022 ​ 37,982 2023 ​ 23,209 2024 ​ 11,292 2025 ​ 9,040 Thereafter ​ 14,804 Total ​ $ 158,927 ​

FINANCIAL INSTRUMENTS AND FAIR

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS	​ NOTE 6—FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS Marketable Debt Securities At December 31, 2020, current available-for-sale marketable debt securities are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ ​ Cost Gains Losses Fair Value ​ ​ (In thousands) Treasury discount notes ​ $ 224,976 ​ $ 3 ​ $ — ​ $ 224,979 Total available-for-sale marketable debt securities ​ $ 224,976 ​ $ 3 ​ $ — ​ $ 224,979 ​ The Company did not hold any marketable debt securities at December 31, 2019. The contractual maturities of debt securities classified as current available-for-sale at December 31, 2020 are within one year . There are no investments in available-for-sale marketable debt securities that have been in a continuous unrealized loss position for longer than twelve months as of December 31, 2020. Investment in MGM Resorts International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Investment in MGM Resorts International (“MGM”) ​ $ 1,860,158 ​ $ — ​ During the year ended December 31, 2020, the Company purchased 59.0 million shares of MGM. The fair value of the investment in MGM is remeasured each reporting period based upon MGM’s closing stock price on the New York Stock Exchange and any unrealized gains or losses are included in the accompanying statement of operations. For the year ended December 31, 2020, the Company recognized an unrealized gain of $840.5 million on its investment in MGM. Long-term Investments Long-term investments consist of: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Equity securities without readily determinable fair values ​ $ 296,491 ​ $ 347,975 Equity method investment ​ 1,152 ​ — Total long-term investments ​ $ 297,643 ​ $ 347,975 ​ Equity Securities without Readily Determinable Fair Values During the first quarter of 2020, the Company recorded unrealized impairments of $ 51.5 million related to certain equity securities without readily determinable fair values due to the impact of COVID-19. All gains and losses on equity securities without readily determinable fair values, realized and unrealized, are recognized in “Other (expense) income, net” in the accompanying statement of operations. The following table presents a summary of unrealized gains and losses recorded in other (expense) income, net, as adjustments to the carrying value of equity securities without readily determinable fair values held as of December 31, 2020 and 2019. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 ​ ​ (In thousands) Upward adjustments (gross unrealized gains) ​ $ — ​ $ 19,698 Downward adjustments including impairments (gross unrealized losses) ​ (51,484) ​ (1,193) Total ​ $ (51,484) ​ $ 18,505 ​ The cumulative upward and downward adjustments (including impairments) to the carrying value of equity securities without readily determinable fair values held at December 31, 2020 were $ 19.7 million and $ 43.5 million, respectively. Realized and unrealized gains and losses for the Company’s marketable equity securities and investments without readily determinable fair values for the years ended December 31, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Realized gains, net, for equity securities sold ​ $ 2,161 ​ $ 22,880 ​ $ 27,366 Unrealized gains, net, on equity securities held ​ 797,565 ​ 18,505 ​ 126,063 Total gains recognized, net ​ $ 799,726 ​ $ 41,385 ​ $ 153,429 ​ Equity Method Investment During the fourth quarter of 2020, the Company acquired 0.3 million common shares of Turo Inc. (“Turo”), a peer-to-peer car sharing marketplace, for approximately $ 1.1 million, which is accounted for under the equity method of accounting on a one quarter lag, given the Company’s preexisting ownership interest of approximately 26.8% on a fully diluted basis in the form of preferred shares, which are not common stock equivalents. Fair Value Measurements The following tables present the Company’s financial instruments that are measured at fair value on a recurring basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Quoted Market ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Prices in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ Total ​ ​ Identical Assets ​ Inputs ​ Inputs ​ Fair Value ​ (Level 1) (Level 2) (Level 3) Measurements ​ ​ (In thousands) Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 1,874,091 ​ $ — ​ $ — ​ $ 1,874,091 Treasury discount notes ​ — ​ 1,224,966 ​ — ​ 1,224,966 Time deposits ​ — ​ 3,265 ​ — ​ 3,265 Marketable debt securities: ​ ​ ​ ​ Treasury discount notes ​ — ​ 224,979 ​ — ​ 224,979 Investment in MGM Resorts International ​ 1,860,158 ​ — ​ — ​ 1,860,158 Other non-current assets: ​ ​ ​ ​ Warrant ​ — ​ — ​ 5,276 ​ 5,276 Total ​ $ 3,734,249 ​ $ 1,453,210 ​ $ 5,276 ​ $ 5,192,735 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Contingent consideration arrangement ​ $ — ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Quoted Market ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Prices in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ Total ​ ​ Identical Assets ​ Inputs ​ Inputs ​ Fair Value ​ (Level 1) (Level 2) (Level 3) Measurements ​ ​ (In thousands) Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 699,589 ​ $ — ​ $ — ​ $ 699,589 Time deposits ​ — ​ 23,075 ​ — ​ 23,075 Other non-current assets: ​ ​ ​ ​ Warrant ​ — ​ — ​ 8,495 ​ 8,495 Total ​ $ 699,589 ​ $ 23,075 ​ $ 8,495 ​ $ 731,159 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Contingent consideration arrangement ​ $ — ​ $ — ​ $ (6,918) ​ $ (6,918) ​ The following table presents the changes in the Company’s financial instruments that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2020 ​ 2019 ​ ​ ​ ​ ​ Contingent ​ ​ ​ ​ Contingent ​ ​ ​ ​ ​ Consideration ​ ​ ​ ​ Consideration ​ Warrant Arrangements Warrant Arrangement ​ ​ (In thousands) Balance at January 1 ​ $ 8,495 ​ $ (6,918) ​ $ — ​ $ (26,657) Fair value at date of acquisition ​ — ​ (1,000) ​ 17,618 ​ — Total net (losses) gains: ​ ​ ​ ​ Included in earnings: ​ ​ ​ ​ Fair value adjustments ​ (3,219) ​ 6,918 ​ (9,123) ​ 19,739 Settlements ​ — ​ 1,000 ​ — ​ — Balance at December 31 ​ $ 5,276 ​ $ — ​ $ 8,495 ​ $ (6,918) ​ Warrant In the third quarter of 2019, the Company made a $ 250 million investment in Turo preferred shares. As part of its investment, the Company received a warrant that is net settleable at the Company’s option and is recorded at fair value each reporting period with any change included in “Other (expense) income, net” in the accompanying statement of operations. The warrant is measured using significant unobservable inputs and is classified in the fair value hierarchy table as Level 3. The warrant is included in “Other non-current assets” in the accompanying balance sheet. Contingent consideration arrangement At December 31, 2020, the Company has one outstanding contingent consideration arrangement related to a business acquisition. The maximum contingent payments related to this arrangement for periods subsequent to December 31, 2020, which is the end of the most recent measurement period, is $ 15.0 million. At December 31, 2020, the Company does not expect to make any payments related to this contingent consideration arrangement. In connection with the Care.com acquisition on February 11, 2020, the Company assumed a contingent consideration arrangement liability of $ 1.0 million, which was subsequently paid and settled during the first quarter of 2020. Generally, our contingent consideration arrangements are based upon financial performance and/or operating metric targets and the Company generally determines the fair value of the contingent consideration arrangements by using probability-weighted analyses to determine the amounts of the gross liability, and, if the arrangements are initially long-term in nature, applying a discount rate that appropriately captures the risks associated with the obligations to determine the net amount reflected in the financial statements. The fair value of contingent consideration arrangements is sensitive to changes in the expected achievement of the applicable targets and changes in discount rates. The Company remeasures the fair value of the contingent consideration arrangements each reporting period, including the accretion of the discount, if applicable, and changes are recognized in “General and administrative expense” in the accompanying statement of operations. There is no contingent consideration liability outstanding at December 31, 2020. The contingent consideration arrangement liability at December 31, 2019 includes a non-current portion of $ 6.9 million and, is included in “Other long-term liabilities” in the accompanying balance sheet. Financial instruments measured at fair value only for disclosure purposes The following table presents the carrying value and the fair value of financial instruments measured at fair value only for disclosure purposes: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ ​ Carrying ​ Fair ​ Carrying ​ Fair ​ Value Value Value Value ​ ​ (In thousands) Notes receivable—related party, current ​ $ — ​ $ — ​ $ 55,251 ​ $ 55,251 Current portion of long-term debt ​ $ — ​ $ — ​ $ (13,750) ​ $ (13,681) Long-term debt, net (a) ​ $ (712,277) ​ $ (725,700) ​ $ (231,946) ​ $ (232,581) (a) At December 31, 2020 and 2019, the carrying value of long-term debt, net includes unamortized original issue discount and debt issuance costs of $ 7.7 million and $ 1.8 million, respectively . At December 31, 2020 and 2019, the fair value of long-term debt, including the current portion, is estimated using observable market prices or indices for similar liabilities, which are Level 2 inputs. ​

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
LONG-TERM DEBT	​ NOTE 7—LONG-TERM DEBT Long-term debt consists of: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) 3.875% ANGI Group Senior Notes due August 15, 2028 (“ANGI Group Senior Notes”); interest payable each February 15 and August 15, commencing February 15, 2021 ​ $ 500,000 ​ $ — ANGI Group Term Loan due November 5, 2023 (“ANGI Group Term Loan”) ​ 220,000 ​ 247,500 Total long-term debt ​ 720,000 ​ 247,500 Less: current portion of ANGI Group Term Loan ​ — ​ 13,750 Less: unamortized debt issuance costs ​ 7,723 ​ 1,804 Total long-term debt, net ​ $ 712,277 ​ $ 231,946 ​ ANGI Group Senior Notes On August 20, 2020, ANGI Group, LLC (“ANGI Group”), a direct wholly-owned subsidiary of ANGI, issued $500 million in aggregate principal amount of the ANGI Group Senior Notes, the proceeds of which are intended for general corporate purposes, including potential future acquisitions and return of capital. At any time prior to August 15, 2023, these notes may be redeemed at a redemption price equal to the sum of the principal amount thereof, plus accrued and unpaid interest and a make-whole premium. Thereafter, these notes may be redeemed at the redemption prices set forth below, plus accrued and unpaid interest thereon, if any, to the applicable redemption date, if redeemed during the twelve-month period beginning on August 15 of the years indicated below: ​ ​ ​ ​ ​ Year Percentage 2023 101.938 % 2024 100.969 % 2025 and thereafter 100.000 % ​ The indenture governing the ANGI Group Senior Notes contains a covenant that would limit ANGI Group’s ability to incur liens for borrowed money in the event a default has occurred or ANGI Group’s secured leverage ratio (as defined in the indenture) exceeds 3.75 to 1.0. At December 31, 2020, there were no limitations pursuant thereto. ANGI Group Term Loan and ANGI Group Revolving Facility ANGI was a party to a credit agreement that terminates on November 5, 2021. The credit agreement governs the ANGI Group Term Loan and revolving credit facility (the “ANGI Group Revolving Facility”), which are collectively referred to as the ANGI Group Credit Agreement. On August 12, 2020, ANGI Group entered into a joinder agreement with ANGI, the other subsidiaries of ANGI that are party to the credit agreement, and each of the other loan parties to the credit agreement, pursuant to which, ANGI Group became the successor borrower under the credit agreement and ANGI Homeservices Inc.’s obligations thereunder were terminated. In addition, on August 12, 2020, the definition of “Permitted Unsecured Ratio Debt” in the credit agreement was amended to remove the requirement that guarantees of certain indebtedness of the borrower be subordinated to the guarantees under the credit agreement. The outstanding balance of the ANGI Group Term Loan was $ 220.0 million and $ 247.5 million, at December 31, 2020 and 2019, respectively. There are quarterly principal payments of $ 3.4 million through December 31, 2021, $ 6.9 million for the one-year period ending December 31, 2022 and $ 10.3 million through maturity of the loan when the final amount of $ 161.6 million is due. Additionally, interest payments are due at least quarterly through the term of the loan. In December 2020, ANGI Group prepaid its required quarterly principal payments for the year ending December 31, 2021 in the aggregate amount of $ 13.8 million. At December 31, 2020 and 2019, the ANGI Group Term Loan bore interest at LIBOR plus 2.00% , or 2.16% and 1.50% or 3.25% , respectively. The spread over LIBOR is subject to change in future periods based on ANGI Group’s consolidated net leverage ratio. The ANGI Group Credit Agreement requires ANGI Group to maintain a consolidated net leverage ratio of not more than 4.5 to 1.0 and a minimum interest coverage ratio of not less than 2.0 to 1.0. The ANGI Group Credit Agreement also contains covenants that would limit ANGI Group’s ability to pay dividends or make distributions in the event a default has occurred or ANGI Group’s consolidated net leverage ratio exceeds 4.25 to 1.0. At December 31, 2020, there were no limitations pursuant thereto. The $ 250 million ANGI Group Revolving Facility expires on November 5, 2023. At December 31, 2020 and 2019, there were no outstanding borrowings under the ANGI Group Revolving Facility. The annual commitment fee on undrawn funds is based on ANGI Group’s consolidated net leverage ratio most recently reported and was 35 and 25 basis points at December 31, 2020 and 2019, respectively. Any future borrowings under the ANGI Group Revolving Facility would bear interest, at ANGI Group’s option, at either a base rate or LIBOR, in each case plus an applicable margin, which is based on ANGI Group’s consolidated net leverage ratio. The financial and other covenants are the same as those for the ANGI Group Term Loan. The ANGI Group Senior Notes, ANGI Group Term Loan and ANGI Group Revolving Facility are guaranteed by certain of ANGI Group’s wholly-owned material domestic subsidiaries and ANGI Group’s obligations under the ANGI Group Term Loan and the ANGI Group Revolving Facility are secured by substantially all assets of ANGI Group and the guarantors, subject to certain exceptions. The ANGI Group Term Loan and outstanding borrowings, if any, under the ANGI Group Revolving Facility rank equally with each other, and have priority over the ANGI Group Senior Notes to the extent of the value of the assets securing the borrowings under the ANGI Group Credit Agreement. Long-term Debt Maturities: Long-term debt maturities as of December 31, 2020 are summarized in the table below: ​ ​ ​ ​ ​ Years Ending December 31, (In thousands) 2022 ​ $ 27,500 2023 ​ 192,500 2028 ​ 500,000 Total ​ 720,000 Less: unamortized debt issuance costs ​ 7,723 Total long-term debt, net ​ $ 712,277 ​

SHAREHOLDERS' EQUITY

SHAREHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
SHAREHOLDERS' EQUITY	​ NOTE 8—SHAREHOLDERS’ EQUITY Description of Common Stock and Class B Convertible Common Stock Except as described herein, shares of IAC common stock and IAC Class B common stock are identical. Each holder of shares of IAC common stock and IAC Class B common stock vote together as a single class with respect to matters that may be submitted to a vote or for the consent of IAC’s shareholders generally, including the election of directors. In connection with any such vote, each holder of IAC common stock is entitled to one vote for each share of IAC common stock held and each holder of IAC Class B common stock is entitled to ten votes for each share of IAC Class B common stock held. Notwithstanding the foregoing, the holders of shares of IAC common stock, acting as a single class, are entitled to elect 25% of the total number of IAC’s directors, and, in the event that 25% of the total number of directors shall result in a fraction of a director, then the holders of shares of IAC common stock, acting as a single class, are entitled to elect the next higher whole number of IAC’s directors. In addition, Delaware law requires that certain matters be approved by the holders of shares of IAC common stock or holders of IAC Class B common stock voting as a separate class. Shares of IAC Class B common stock are convertible into shares of IAC common stock at the option of the holder thereof, at any time, on a share-for-share basis. Such conversion ratio will in all events be equitably preserved in the event of any recapitalization of IAC by means of a stock dividend on, or a stock split or combination of, outstanding shares of IAC common stock or IAC Class B common stock, or in the event of any merger, consolidation or other reorganization of IAC with another corporation. Upon the conversion of shares of IAC Class B common stock into shares of IAC common stock, those shares of IAC Class B common stock will be retired and will not be subject to reissue. Shares of IAC common stock are not convertible into shares of IAC Class B common stock. The holders of shares of IAC common stock and the holders of shares of IAC Class B common stock are entitled to receive, share for share, such dividends as may be declared by IAC’s Board of Directors out of funds legally available therefor. In the event of a liquidation, dissolution, distribution of assets or winding-up of IAC, the holders of shares of IAC common stock and the holders of shares of IAC Class B common stock are entitled to receive, share for share, all the assets of IAC available for distribution to its stockholders, after the rights of the holders of any IAC preferred stock have been satisfied. Common Stock Repurchases On June 30, 2020, the Board of Directors of the Company authorized repurchases up to 8.0 million shares of common stock, which is equal to the number of shares that were available under the repurchase authorization at Old IAC immediately prior to the MTCH Separation. For the period subsequent to the MTCH Separation through December 31, 2020 there we no repurchases of IAC common stock.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	​ NOTE 9—ACCUMULATED OTHER COMPREHENSIVE LOSS The following tables present the components of accumulated other comprehensive (loss) income and items reclassified out of accumulated other comprehensive loss into earnings: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ ​ ​ Unrealized Gains ​ ​ ​ ​ ​ Foreign ​ On Available- ​ Accumulated ​ ​ Currency ​ For-Sale ​ Other ​ ​ Translation ​ Marketable Debt ​ Comprehensive ​ Adjustment Securities (Loss) Income ​ ​ (In thousands) Balance at January 1 ​ $ (12,226) ​ $ — ​ $ (12,226) Other comprehensive income before reclassifications ​ 6,236 ​ 2 ​ 6,238 Amounts reclassified to earnings ​ (144) ​ — ​ (144) Net current period other comprehensive income ​ 6,092 ​ 2 ​ 6,094 Accumulated other comprehensive income allocated to noncontrolling interests during the period ​ (38) ​ — ​ (38) Balance at December 31 ​ $ (6,172) ​ $ 2 ​ $ (6,170) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ ​ ​ Unrealized Gains ​ ​ ​ ​ ​ Foreign ​ On Available- ​ Accumulated ​ ​ Currency ​ For-Sale ​ Other ​ ​ Translation ​ Marketable Debt ​ Comprehensive ​ Adjustment Securities (Loss) Income ​ ​ (In thousands) Balance at January 1 ​ $ (12,543) ​ $ 2 ​ $ (12,541) Other comprehensive income (loss) ​ 337 ​ (2) ​ 335 Net current period other comprehensive income (loss) ​ 337 ​ (2) ​ 335 Accumulated other comprehensive income allocated to noncontrolling interests during the period ​ (20) ​ — ​ (20) Balance at December 31 ​ $ (12,226) ​ $ — ​ $ (12,226) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2018 ​ ​ ​ ​ ​ Unrealized Gains ​ ​ ​ ​ ​ Foreign ​ On Available- ​ Accumulated ​ ​ Currency ​ For-Sale ​ Other ​ ​ Translation ​ Marketable Debt ​ Comprehensive ​ Adjustment Securities Loss ​ ​ (In thousands) Balance at January 1 ​ $ (7,504) ​ $ — ​ $ (7,504) Other comprehensive (loss) income before reclassifications ​ (4,976) ​ 2 ​ (4,974) Amounts reclassified to earnings ​ (52) ​ — ​ (52) Net current period other comprehensive (loss) income ​ (5,028) ​ 2 ​ (5,026) Accumulated other comprehensive income allocated to noncontrolling interests during the period ​ (11) ​ — ​ (11) Balance at December 31 ​ $ (12,543) ​ $ 2 ​ $ (12,541) ​ The amounts reclassified out of foreign currency translation adjustment into earnings for the years ended December 31, 2020 and 2018 relate to the liquidation of international subsidiaries. At December 31, 2020, 2019 and 2018, there was no tax benefit of provision on the accumulated other comprehensive loss. ​

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
EARNINGS PER SHARE	NOTE 10—EARNINGS PER SHARE The following table sets forth the computation of basic and diluted earnings per share attributable to IAC shareholders: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 ​ Basic Diluted Basic Diluted Basic Diluted ​ ​ (In thousands, except per share data) Numerator: ​ ​ ​ ​ ​ ​ Net earnings ​ $ 268,586 ​ $ 268,586 ​ $ 32,183 ​ $ 32,183 ​ $ 292,371 ​ $ 292,371 Net loss (earnings) attributable to noncontrolling interests ​ 1,140 ​ 1,140 ​ (9,288) ​ (9,288) ​ (45,599) ​ (45,599) Impact from public subsidiaries’ dilutive securities (a) ​ — ​ 71 ​ — ​ — ​ — ​ — Net earnings attributable to IAC shareholders ​ $ 269,726 ​ $ 269,797 ​ $ 22,895 ​ $ 22,895 ​ $ 246,772 ​ $ 246,772 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: ​ ​ ​ ​ ​ ​ Weighted average basic shares outstanding (b) ​ 85,355 ​ 85,355 ​ 85,132 ​ 85,132 ​ 85,132 ​ 85,132 Dilutive securities (a) (c) (d) (e) ​ — ​ 5,593 ​ — ​ — ​ — ​ — Denominator for earnings per share—weighted average shares (a) (c) (d) (e) ​ 85,355 ​ 90,948 ​ 85,132 ​ 85,132 ​ 85,132 ​ 85,132 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share attributable to IAC shareholders: ​ ​ ​ ​ ​ ​ Earnings per share ​ $ 3.16 ​ $ 2.97 ​ $ 0.27 ​ $ 0.27 ​ $ 2.90 ​ $ 2.90 (a) IAC has the option to settle certain ANGI stock-based awards in its shares. For the year ended December 31, 2020, it is more dilutive for IAC to settle these ANGI equity awards. (b) On November 5, 2020, the Company granted 3,000,000 shares of IAC restricted common stock to its Chief Executive Officer (“CEO”), that cliff vest on the ten-year anniversary of the grant date based on satisfaction of IAC’s stock price targets and continued employment through the vesting date. These shares are included in common stock outstanding at December 31, 2020 on the balance sheet, however, are excluded from weighted average basic shares outstanding in the table above in calculating earnings per share for the year ended December 31, 2020. (c) If the effect is dilutive, weighted average common shares outstanding include the incremental shares that would be issued upon the assumed exercise of stock options and subsidiary denominated equity, vesting of restricted common stock, restricted stock units (“RSUs”) and market-based awards (“MSUs”). For the year ended December 31, 2020, 3.1 million potentially dilutive securities were excluded from the calculation of diluted earnings per share because their inclusion would have been anti-dilutive. (d) The Company computed basic and diluted earnings per share for periods prior to the MTCH Separation using the shares issued on June 30, 2020 in connection with the MTCH Separation. (e) See “Note 11—Stock-based Compensation” for additional information on the grant of IAC restricted common stock to its CEO and equity instruments denominated in the shares of certain subsidiaries .

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	NOTE 11—STOCK-BASED COMPENSATION IAC Denominated Stock-based Awards IAC currently has one active plan under which stock-based awards denominated in shares of IAC common stock have been and may be granted. There are also outstanding stock-based awards that were granted under older plans that have since expired or been discontinued. The active plan provides for grants of stock options to acquire shares of IAC common stock, RSUs denominated in shares of IAC common stock, including those that may be linked to the achievement of the Company’s stock price, known as market-based awards (“MSUs”) and those that may be linked to the achievement of a performance target, known as performance-based awards (“PSUs”), restricted stock, as well as other equity awards. The plan authorizes the Company to grant awards to its employees, officers, directors and consultants. At December 31, 2020, there are 31.1 million shares of stock reserved for future issuance under this plan. This number reflects an adjustment to the number of shares originally authorized under the plan made in connection with the MTCH Separation and pursuant to the plan terms. This plan was an Old IAC plan and was adopted by the Company and became effective upon the consummation of the MTCH Separation. The plan has a stated term of ten years and provides that the exercise price of stock options granted will not be less than the market price of the Company’s common stock on the grant date. The plan does not specify grant dates or vesting schedules of awards as those determinations have been delegated to the Compensation and Human Resources Committee of IAC’s Board of Directors (the “Committee”). Each grant agreement reflects the vesting schedule for that particular grant as determined by the Committee. RSU awards currently outstanding generally cliff-vest after a five-year period, vest in equal annual installments over a four-year period or cliff-vest after a three-year period in each case, from the grant date. All outstanding stock options are fully vested. There are no MSU or PSU awards currently outstanding at December 31, 2020. The restricted stock award currently outstanding cliff vest on the ten-year anniversary of the November 5, 2020 grant date based on the satisfaction of IAC stock price targets and continued employment through the vesting date. The amount of stock-based compensation expense recognized in the statement of operations is net of estimated forfeitures. The forfeiture rate is estimated at the grant date based on historical experience and revised, if necessary, in subsequent periods if actual forfeitures differ from the estimated rate. The expense ultimately recorded is for the awards that vest. At December 31, 2020, there is $398.3 million of unrecognized compensation cost, net of estimated forfeitures, related to all equity-based awards, which is expected to be recognized over a weighted average period of approximately 6.2 years. The total income tax benefit recognized in the accompanying statement of operations for the years ended December 31, 2020, 2019 and 2018 related to all stock-based compensation is $204.3 million, $82.4 million and $80.7 million, respectively. The aggregate income tax benefit recognized related to the exercise of stock options for the years ended December 31, 2020, 2019 and 2018, is $170.1 million, $64.2 million, and $63.6 million, respectively. As the Company is currently in a NOL position, there will be some delay in the timing of the realization of the cash benefit of the income tax deductions related to stock-based compensation because it will be dependent upon the amount and timing of future taxable income and the timing of estimated income tax payments. IAC Restricted Common Stock On November 5, 2020, the Company entered into a new, ten-year employment agreement and a Restricted Stock Agreement (“RSA Agreement”) with Joseph Levin, IAC’s Chief Executive Officer. The RSA Agreement provides for a grant of 3,000,000 shares of IAC restricted common stock that cliff vest on the ten-year anniversary of the grant date based on satisfaction of IAC’s stock price targets and Mr. Levin’s continued employment through the vesting date. Mr. Levin may request an extension of the measurement and vesting period from 10 to 12 years and IAC will consider the request in light of the circumstances. Mr. Levin may elect to accelerate vesting of the IAC restricted shares, effective on the 6 th , 7 th , 8 th , or 9 th anniversary of the grant date, in which case performance will be measured through such date, and Mr. Levin will receive a pro-rated portion of the award (based on the years elapsed from the grant date) and any remaining shares will be forfeited. The applicable stock price goals are proportionately lower on the earlier vesting dates. The value of restricted common stock grant was estimated using a lattice model that incorporates a Monte Carlo simulation of IAC’s stock price. The fair value of the restricted common stock grant on November 5, 2020 was $61.06 per share. The total grant date fair value of the award was $183.2 million. IAC Restricted Stock Units and Market-based Stock Units RSUs and MSUs are awards in the form of phantom shares or units denominated in a hypothetical equivalent number of shares of IAC common stock and with the value of each RSU equal to the fair value of IAC common stock at the date of grant. The value of each MSU is estimated using a lattice model that incorporates a Monte Carlo simulation of IAC’s stock price. Each RSU grant is subject to service-based vesting, where a specific period of continued employment must pass before an award vests. The vesting of MSUs is tied to the stock price of IAC. For RSU grants, the expense is measured at the grant date as the fair value of IAC common stock and expensed as stock-based compensation over the vesting term. MSU grants are expensed over the shorter of the vesting period or the derived service period. Unvested RSUs and MSUs outstanding at December 31, 2020 and changes during the period ended December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ RSUs ​ MSUs ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ Average ​ ​ Number ​ Grant Date ​ Number ​ Grant Date ​ of Shares Fair Value of Shares Fair Value ​ ​ (Shares in thousands) Unvested on June 30, 2020, the date of the MTCH Separation 421 ​ $ 48.13 347 ​ $ 44.76 Granted 1,121 ​ 128.82 — ​ — Vested (26) ​ 64.52 (347) ​ 44.76 Forfeited (13) ​ 94.17 — ​ — Unvested at December 31, 2020 1,503 ​ $ 107.62 — ​ $ — ​ In connection with the MTCH Separation, Old IAC’s RSUs were converted into IAC RSUs in a manner that preserved their fair value immediately before and immediately after the conversion. These equity awards are settled on a net basis, with the award holder entitled to receive IAC shares equal to the number of RSUs vesting less a number of shares with a value equal to the required cash tax withholding payment, which will be paid by the Company. The number of IAC common shares that would be required to net settle RSUs outstanding at January 29, 2021 is 0.7 million shares. In addition, withholding taxes, which will be paid by the Company on behalf of the employees upon vest, would have been $152.7 million at January 29, 2021, assuming a 50% withholding rate. The weighted average fair value of RSUs granted subsequent to the MTCH Separation through December 31, 2020 based on market prices of IAC’s common stock on the grant date was $128.82 . There were no MSUs granted subsequent to the MTCH Separation through December 31, 2020. The total fair value of RSUs and MSUs that vested subsequent to the MTCH Separation through December 31, 2020 was $3.8 million and $43.6 million. IAC Stock Options Stock options outstanding at December 31, 2020 and changes during the period ended December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ Shares Price Term in Years Value ​ ​ (Shares and intrinsic value in thousands) Old IAC options converted into IAC options on June 30, 2020, the date of the MTCH Separation 4,498 ​ $ 20.08 ​ Granted — ​ — ​ Exercised (587) ​ 13.46 ​ Forfeited — ​ — ​ Expired (2) ​ 14.05 ​ Options outstanding at December 31, 2020 3,909 ​ $ 21.08 4.9 ​ $ 657,704 Options exercisable 3,909 ​ $ 21.08 4.9 ​ $ 657,704 ​ In connection with the MTCH Separation, Old IAC denominated stock options were converted into stock options to purchase IAC common stock and stock options to purchase New Match common stock in a manner that preserved the spread value of the stock options immediately before and immediately after the adjustment, with the allocation between the two stock options based on the value of a share of IAC common stock relative to the value of a share of New Match common stock multiplied by the transaction exchange ratio of 2.1584 . The aggregate intrinsic value in the table above represents the difference between IAC’s closing stock price on the last trading day of 2020 and the exercise price, multiplied by the number of in-the-money options that would have been exercised had all option holders exercised their options on December 31, 2020. The total intrinsic value of IAC stock options exercised subsequent to the MTCH Separation through December 31, 2020 is $74.8 million. The following table summarizes the information about stock options outstanding and exercisable at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ Options Exercisable ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ Average ​ Weighted- ​ ​ ​ Average ​ Weighted- ​ ​ Outstanding at ​ Remaining ​ Average ​ Exercisable at ​ Remaining ​ Average ​ ​ December 31, ​ Contractual ​ Exercise ​ December 31, ​ Contractual ​ Exercise Range of Exercise Prices 2020 Life in Years Price 2020 Life in Years Price ​ ​ (Shares in thousands) Less than $20.00 1,060 4.7 ​ $ 14.21 1,060 4.7 ​ $ 14.21 $20.01 to $30.00 2,765 4.9 ​ 22.96 2,765 4.9 ​ 22.96 $30.01 to $40.00 4 6.6 ​ 31.82 4 6.6 ​ 31.82 $40.01 to $50.00 80 7.2 ​ 46.61 80 7.2 ​ 46.61 ​ 3,909 4.9 ​ $ 21.08 3,909 4.9 ​ $ 21.08 ​ The fair value of stock option awards, with the exception of market-based awards, is estimated on the grant date using the Black-Scholes option pricing model. The Black-Scholes option pricing model incorporates various assumptions, including expected volatility, risk-free interest rate and expected term. The Company has the discretion to settle IAC stock options net of withholding tax and exercise price or require the award holder to pay its share of the withholding tax, which he or she may do so by selling IAC common shares. The aggregate intrinsic value of IAC’s stock options outstanding as of January 29, 2021, is $737.9 million. Assuming all stock options outstanding on January 29, 2021 were net settled on that date, the Company would have issued 1.8 million common shares and would have remitted $369.0 million in cash for withholding taxes (assuming a 50% withholding rate). Assuming all stock options outstanding on January 29, 2021 were settled through the issuance of a number of IAC common shares equal to the number of stock options exercised, the Company would have issued 3.9 million common shares and would have received $82.3 million in cash proceeds. Stock-based Awards Denominated in the Shares of Certain Subsidiaries Non-publicly-traded Subsidiaries The following description excludes awards denominated in ANGI shares. The Company has granted stock settled stock appreciation rights to employees and management that are denominated in the equity of certain non-publicly traded subsidiaries of the Company. These equity awards vest over a period of years or upon the occurrence of certain prescribed events. The value of the stock settled stock appreciation rights is tied to the value of the common stock of these subsidiaries. Accordingly, these interests only have value to the extent the relevant business appreciates in value above the initial value utilized to determine the exercise price. These interests can have significant value in the event of significant appreciation. The fair value of these interest is generally determined by negotiation or arbitration when settled, which will occur at various dates through 2026. These equity awards are settled on a net basis, with the award holder entitled to receive a payment in IAC common shares equal to the intrinsic value of the award at exercise less an amount equal to the required cash tax withholding payment, which will be paid by the Company. The number of IAC common shares ultimately needed to settle these awards may vary significantly from the estimated number below as a result of both movements in our stock price and a determination of fair value of the relevant subsidiary that is different than our estimate. The expense associated with these equity awards is initially measured at fair value at the grant date and is expensed as stock-based compensation over the vesting term. The number of IAC common shares that would be required to settle these interests at current estimated fair values, including vested and unvested interests, at January 29, 2021 is 0.1 million shares. Withholding taxes, which will be paid by the Company on behalf of the employees upon exercise, would have been $12.5 million at January 29, 2021, assuming a 50% withholding rate. Excluded from these amounts are awards related to Vimeo, for which the aggregate intrinsic value of outstanding Vimeo awards as of January 29, 2021, assuming a per share price of $35.35 , which is equal to the per share price of Vimeo based upon a $5.7 billion pre-money valuation, is $405.1 million. Withholding taxes would have been $202.6 million at January 29, 2021, assuming a 50% withholding rate. If the Spin-off is completed, these awards will be settled in shares of SpinCo common stock. SpinCo management will have the discretion to continue to net settle these awards, or require the award holder to pay its share of the withholding tax, which he or she may do so by selling SpinCo common shares. ANGI ANGI currently settles all of its equity awards on a net basis. Certain ANGI stock appreciation rights issued prior to the Combination are settleable in either shares of ANGI common stock or shares of IAC common stock at IAC’s option. If settled in IAC common stock, ANGI reimburses IAC in shares of its common stock. The aggregate intrinsic value of these awards outstanding at January 29, 2021 is $92.1 million, assuming these awards were net settled on that date, the withholding taxes that would be payable by ANGI are $46.1 million, assuming a 50% withholding rate, and ANGI would have issued 3.3 million shares. Certain equity awards denominated in shares of ANGI’s subsidiaries may be settled in either shares of ANGI common stock or IAC common stock at IAC’s option. To the extent shares of IAC common stock are issued in settlement of these awards, ANGI is obligated to reimburse IAC for the cost of those shares by issuing shares of ANGI common stock. The aggregate intrinsic value of all other ANGI equity awards, including stock options, RSUs and subsidiary denominated equity at January 29, 2021 is $162.2 million; assuming these awards were net settled on that date, the withholding taxes that would be payable are $81.1 million, assuming a 50% withholding rate, and ANGI would have issued 5.8 million shares of its common stock. Modification of awards During 2020, the Company modified certain equity awards in connection with the MTCH Separation and recognized a modification charge of $56.9 million, of which $56.0 million was recognized as stock-based compensation expense in the year ended December 31, 2020 and the remaining charge will be recognized over the vesting period of the modified awards. In addition, certain other equity awards were modified during 2020 resulting in modification charges of $20.5 million in the aggregate, of which $14.1 million was recorded by ANGI. During 2019, certain equity awards were modified resulting in modification charges of $13.1 million. During 2018, certain equity awards were modified resulting in modification charges of $11.8 million, of which $3.9 million was recorded by ANGI. In connection with the Combination in 2017, the previously issued HomeAdvisor (US) stock appreciation rights were converted into ANGI equity awards resulting in a modification charge of $217.7 million of which $21.1 million, $29.0 million, and $56.9 million were recognized as stock-based compensation expense in the years ended December 31, 2020, 2019, and 2018 respectively. At December 31, 2020, there is $0.9 million of expense remaining related to this modification that will be recognized over the remaining vesting period of the modified awards. ​

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	NOTE 12—SEGMENT INFORMATION The overall concept that the Company employs in determining its operating segments is to present the financial information in a manner consistent with: how the chief operating decision maker views the businesses. In addition, we consider how the businesses are organized as to segment management and the focus of the businesses with regards to the types of services or products offered or the target market. Operating segments are combined for reporting purposes if they meet certain aggregation criteria, which principally relate to the similarity of their economic characteristics, which is the case for the Desktop and Ask Media Group operating segments in the Search reportable segment, or, in the case of the Emerging & Other reportable segment, do not meet the quantitative thresholds that require presentation as separate reportable segments. The following table presents revenue by reportable segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Revenue: ​ ​ ​ ANGI Homeservices ​ $ 1,467,925 ​ $ 1,326,205 ​ $ 1,132,241 Vimeo ​ 283,218 ​ 196,015 ​ 159,641 Dotdash ​ 213,753 ​ 167,594 ​ 130,991 Search ​ 613,274 ​ 742,184 ​ 823,950 Emerging & Other ​ 469,759 ​ 274,107 ​ 286,586 Inter-segment eliminations ​ (248) ​ (304) ​ (361) Total ​ $ 3,047,681 ​ $ 2,705,801 ​ $ 2,533,048 ​ The following table presents the revenue of the Company’s segments disaggregated by type of service: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) ANGI Homeservices ​ ​ ​ Marketplace: ​ ​ ​ Consumer connection revenue (a) ​ $ 1,054,660 ​ $ 913,533 ​ $ 704,341 Service professional membership subscription revenue ​ 50,975 ​ 63,872 ​ 66,214 Other revenue ​ 25,685 ​ 15,263 ​ 3,940 Total Marketplace revenue ​ 1,131,320 ​ 992,668 ​ 774,495 Advertising and other revenue (b) ​ 264,108 ​ 257,224 ​ 287,676 Total North America revenue ​ 1,395,428 ​ 1,249,892 ​ 1,062,171 Consumer connection revenue (c) ​ 57,692 ​ 59,611 ​ 50,913 Service professional membership subscription revenue ​ 13,091 ​ 14,231 ​ 17,362 Advertising and other revenue ​ 1,714 ​ 2,471 ​ 1,795 Total Europe revenue ​ 72,497 ​ 76,313 ​ 70,070 Total ANGI Homeservices revenue ​ $ 1,467,925 ​ $ 1,326,205 ​ $ 1,132,241 (a) Includes fees paid by service professionals for consumer matches and revenue from pre-priced jobs sourced through the HomeAdvisor and Handy platforms. (b) Includes Angie’s List revenue from service professionals under contract for advertising and Angie’s List membership subscription fees from consumers, as well as revenue from mHelpDesk, HomeStars, and Felix. Felix was sold on December 31, 2018 and its revenue for the year ended December 31, 2018 was $36.9 million. (c) Includes fees paid by service professionals for consumer matches. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 ​ (In thousands) Vimeo ​ ​ ​ ​ ​ ​ ​ ​ ​ Platform revenue ​ $ 283,218 $ 193,736 $ 146,665 Hardware revenue ​ — ​ 2,279 ​ 12,976 Total Vimeo revenue ​ $ 283,218 ​ $ 196,015 ​ $ 159,641 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Dotdash ​ ​ ​ Display advertising revenue ​ $ 137,455 ​ $ 126,350 ​ $ 103,704 Performance marketing revenue ​ 76,298 ​ 41,244 ​ 27,287 Total Dotdash revenue ​ $ 213,753 ​ $ 167,594 ​ $ 130,991 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Search ​ ​ ​ Advertising revenue: ​ ​ ​ Google advertising revenue ​ $ 506,077 ​ $ 678,438 ​ $ 770,494 Non-Google advertising revenue ​ 90,286 ​ 47,583 ​ 31,975 Total advertising revenue ​ 596,363 ​ 726,021 ​ 802,469 Other revenue ​ 16,911 ​ 16,163 ​ 21,481 Total Search revenue ​ $ 613,274 ​ $ 742,184 ​ $ 823,950 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Emerging & Other ​ ​ ​ Subscription revenue ​ $ 303,482 ​ $ 194,362 ​ $ 102,592 Marketplace revenue ​ 138,726 ​ 38,950 ​ 19,665 Advertising revenue: ​ ​ ​ Non-Google advertising revenue ​ 16,236 ​ 23,372 ​ 64,319 Google advertising revenue ​ 3,130 ​ 4,486 ​ 14,393 Total advertising revenue ​ 19,366 ​ 27,858 ​ 78,712 Service revenue ​ 4,410 ​ 3,881 ​ 22,142 Media production and distribution revenue ​ 3,585 ​ 8,897 ​ 61,717 Other revenue ​ 190 ​ 159 ​ 1,758 Total Emerging & Other revenue ​ $ 469,759 ​ $ 274,107 ​ $ 286,586 ​ Revenue by geography is based on where the customer is located. Geographic information about revenue and long-lived assets is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Revenue: ​ ​ ​ United States ​ $ 2,449,257 ​ $ 2,097,743 ​ $ 1,951,957 All other countries ​ 598,424 ​ 608,058 ​ 581,091 Total ​ $ 3,047,681 ​ $ 2,705,801 ​ $ 2,533,048 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Long-lived assets (excluding goodwill, intangible assets and ROU assets): ​ ​ United States ​ $ 266,169 ​ $ 297,433 All other countries ​ 12,082 ​ 7,981 Total ​ $ 278,251 ​ $ 305,414 ​ The following tables present operating income (loss) and Adjusted EBITDA by reportable segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Operating (loss) income: ​ ​ ​ ANGI Homeservices ​ $ (6,368) ​ $ 38,645 ​ $ 63,906 Vimeo ​ (26,392) ​ (51,921) ​ (35,594) Dotdash ​ 50,241 ​ 29,021 ​ 18,778 Search ​ (248,711) ​ 122,347 ​ 151,425 Emerging & Other ​ (70,896) ​ (21,790) ​ (26,627) Corporate ​ (270,223) ​ (166,751) ​ (136,053) Total ​ $ (572,349) ​ $ (50,449) ​ $ 35,835 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Adjusted EBITDA: (d) ​ ​ ​ ANGI Homeservices ​ $ 172,804 ​ $ 202,297 ​ $ 247,506 Vimeo ​ $ (11,187) ​ $ (41,790) ​ $ (28,045) Dotdash ​ $ 66,206 ​ $ 39,601 ​ $ 21,384 Search ​ $ 51,344 ​ $ 124,163 ​ $ 182,905 Emerging & Other ​ $ (37,699) ​ $ (28,368) ​ $ (14,889) Corporate ​ $ (147,502) ​ $ (88,617) ​ $ (74,011) (d) The Company’s primary financial measure is Adjusted EBITDA, which is defined as operating income excluding: (1) stock-based compensation expense; (2) depreciation; and (3) acquisition-related items consisting of (i) amortization of intangible assets and impairments of goodwill and intangible assets, if applicable, and (ii) gains and losses recognized on changes in the fair value of contingent consideration arrangements. The Company believes this measure is useful for analysts and investors as this measure allows a more meaningful comparison between the Company’s performance and that of its competitors. The above items are excluded from the Company’s Adjusted EBITDA measure because these items are non-cash in nature. Adjusted EBITDA has certain limitations because it excludes the impact of these expenses. The following tables reconcile operating (loss) income for the Company’s reportable segments and net earnings attributable to IAC shareholders to Adjusted EBITDA: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquisition- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ related Contingent ​ ​ ​ ​ ​ ​ ​ Operating Stock-Based ​ ​ ​ ​ Consideration ​ ​ ​ ​ ​ ​ (Loss) ​ Compensation ​ ​ ​ ​ Amortization ​ Fair Value ​ Goodwill ​ ​ ​ ​ ​ Income ​ Expense ​ Depreciation ​ of Intangibles ​ Adjustments ​ Impairment ​ Adjusted EBITDA ​ ​ (In thousands) ANGI Homeservices ​ $ (6,368) ​ $ 83,649 ​ $ 52,621 ​ $ 42,902 ​ $ — ​ $ — ​ $ 172,804 Vimeo ​ (26,392) ​ $ — ​ $ 460 ​ $ 14,745 ​ $ — ​ $ — ​ $ (11,187) Dotdash ​ 50,241 ​ $ — ​ $ 1,794 ​ $ 14,171 ​ $ — ​ $ — ​ $ 66,206 Search ​ (248,711) ​ $ — ​ $ 2,709 ​ $ 32,200 ​ $ — ​ $ 265,146 ​ $ 51,344 Emerging & Other ​ (70,896) ​ $ 100 ​ $ 2,449 ​ $ 37,566 ​ $ (6,918) ​ $ — ​ $ (37,699) Corporate ​ (270,223) ​ $ 113,471 ​ $ 9,250 ​ $ — ​ $ — ​ $ — ​ $ (147,502) Total ​ (572,349) ​ ​ ​ ​ ​ ​ Interest expense ​ (16,166) ​ ​ ​ ​ ​ ​ Unrealized gain on investment in MGM Resorts International ​ 840,550 ​ ​ ​ ​ ​ ​ Other expense, net ​ (42,468) ​ ​ ​ ​ ​ ​ Earnings before income taxes ​ 209,567 ​ ​ ​ ​ ​ ​ Income tax benefit ​ 59,019 ​ ​ ​ ​ ​ ​ Net earnings ​ 268,586 ​ ​ ​ ​ ​ ​ Net loss attributable to noncontrolling interests ​ 1,140 ​ ​ ​ ​ ​ ​ Net earnings attributable to IAC shareholders ​ $ 269,726 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquisition- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ related Contingent ​ ​ ​ ​ ​ ​ ​ Operating Stock-based ​ ​ ​ ​ Consideration ​ ​ ​ ​ ​ ​ Income ​ Compensation ​ ​ ​ ​ Amortization ​ Fair Value ​ Goodwill ​ Adjusted ​ ​ (Loss) ​ Expense ​ Depreciation ​ of Intangibles ​ Arrangements ​ Impairment ​ EBITDA ​ ​ (In thousands) ANGI Homeservices ​ $ 38,645 ​ $ 68,255 ​ $ 39,915 ​ $ 55,482 ​ $ — ​ $ — ​ $ 202,297 Vimeo ​ ​ (51,921) ​ $ — ​ $ 478 ​ $ 9,653 ​ $ — ​ $ — ​ $ (41,790) Dotdash ​ 29,021 ​ $ — ​ $ 974 ​ $ 9,606 ​ $ — ​ $ — ​ $ 39,601 Search ​ 122,347 ​ $ — ​ $ 1,816 ​ $ — ​ $ — ​ $ — ​ $ 124,163 Emerging & Other ​ (21,790) ​ $ — ​ $ 715 ​ $ 9,127 ​ $ (19,738) ​ $ 3,318 ​ $ (28,368) Corporate ​ (166,751) ​ $ 66,083 ​ $ 12,051 ​ $ — ​ $ — ​ $ — ​ $ (88,617) Total ​ (50,449) ​ ​ ​ ​ ​ ​ Interest expense ​ (11,904) ​ ​ ​ ​ ​ ​ Other income, net ​ 34,047 ​ ​ ​ ​ ​ ​ Loss before income taxes ​ (28,306) ​ ​ ​ ​ ​ ​ Income tax benefit ​ 60,489 ​ ​ ​ ​ ​ ​ Net earnings ​ 32,183 ​ ​ ​ ​ ​ ​ Net earnings attributable to noncontrolling interests ​ (9,288) ​ ​ ​ ​ ​ ​ Net earnings attributable to IAC shareholders ​ $ 22,895 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquisition- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ related Contingent ​ ​ ​ ​ Operating ​ Stock-Based ​ ​ ​ ​ Consideration ​ ​ ​ ​ Income ​ Compensation ​ ​ ​ ​ Amortization ​ Fair Value ​ ​ ​ ​ ​ (Loss) Expense ​ Depreciation ​ of Intangibles ​ Adjustments ​ Adjusted EBITDA ​ ​ (In thousands) ANGI Homeservices ​ $ 63,906 ​ $ 97,078 ​ $ 24,310 ​ $ 62,212 ​ $ — ​ $ 247,506 Vimeo ​ (35,594) ​ $ — ​ $ 1,200 ​ $ 6,349 ​ $ — ​ $ (28,045) Dotdash ​ 18,778 ​ $ — ​ $ 969 ​ $ 1,637 ​ $ — ​ $ 21,384 Search ​ 151,425 ​ $ — ​ $ 3,311 ​ $ 28,169 ​ $ — ​ $ 182,905 Emerging & Other ​ (26,627) ​ $ 919 ​ $ 969 ​ $ 8,714 ​ $ 1,136 ​ $ (14,889) Corporate ​ (136,053) ​ $ 50,408 ​ $ 11,634 ​ $ — ​ $ — ​ $ (74,011) Total ​ 35,835 ​ ​ ​ ​ ​ Interest expense ​ (13,059) ​ ​ ​ ​ ​ Other income, net ​ 282,795 ​ ​ ​ ​ ​ Earnings before income taxes ​ 305,571 ​ ​ ​ ​ ​ Income tax provision ​ (13,200) ​ ​ ​ ​ ​ Net earnings ​ 292,371 ​ ​ ​ ​ ​ Net earnings attributable to noncontrolling interests ​ (45,599) ​ ​ ​ ​ ​ Net earnings attributable to IAC shareholders ​ $ 246,772 ​ ​ ​ ​ ​ ​ The following table presents capital expenditures by reportable segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Capital expenditures: ​ ​ ​ ANGI Homeservices ​ $ 52,488 ​ $ 68,804 ​ $ 46,976 Vimeo ​ 844 ​ 2,801 ​ 209 Dotdash ​ 5,445 ​ — ​ 102 Search ​ 47 ​ 43 ​ 479 Emerging & Other ​ 1,363 ​ 387 ​ 751 Corporate ​ 1,383 ​ 25,863 ​ 6,163 Total ​ $ 61,570 ​ $ 97,898 ​ $ 54,680 ​

LEASES

LEASES	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
LEASES	NOTE 13—LEASES The Company leases land, office space, data center facilities and equipment used in connection with its operations under various operating leases, the majority of which contain escalation clauses. ROU assets represent the Company’s right to use the underlying assets for the lease term and lease liabilities represent the present value of the Company’s obligation to make payments arising from these leases. ROU assets and related lease liabilities are based on the present value of fixed lease payments over the lease term using the Company’s and its publicly-traded subsidiary’s respective incremental borrowing rates on the lease commencement date or January 1, 2019 for leases that commenced prior to that date. The Company combines the lease and non-lease components of lease payments in determining ROU assets and related lease liabilities. If the lease includes one or more options to extend the term of the lease, the renewal option is considered in the lease term if it is reasonably certain the Company will exercise the option(s). Lease expense is recognized on a straight-line basis over the term of the lease. As permitted by ASC 842, leases with an initial term of twelve months or less (“short-term leases”) are not recorded on the accompanying balance sheet. Variable lease payments consist primarily of common area maintenance, utilities and taxes, which are not included in the recognition of ROU assets and related lease liabilities. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Leases Balance Sheet Classification 2020 2019 ​ ​ ​ ​ (In thousands) Assets: ​ ​ Right-of-use assets Other non-current assets ​ $ 171,741 ​ $ 138,608 ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ Current lease liabilities Accrued expenses and other current liabilities ​ $ 27,785 ​ $ 23,188 Long-term lease liabilities Other long-term liabilities ​ 206,389 ​ 168,321 Total lease liabilities ​ $ 234,174 ​ $ 191,509 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Lease Expense Income Statement Classification 2020 2019 ​ ​ ​ ​ (In thousands) Fixed lease expense Cost of revenue ​ $ 2,214 ​ $ 547 Fixed lease expense Selling and marketing expense ​ 12,779 ​ 10,613 Fixed lease expense General and administrative expense ​ 21,433 ​ 17,751 Fixed lease expense Product development expense ​ 3,456 ​ 1,502 Total fixed lease expense (a) ​ 39,882 ​ 30,413 Variable lease expense Cost of revenue ​ — ​ 83 Variable lease expense Selling and marketing expense ​ 2,314 ​ 1,573 Variable lease expense General and administrative expense ​ 7,452 ​ 5,729 Variable lease expense Product development expense ​ 939 ​ 391 Total variable lease expense ​ 10,705 ​ 7,776 Net lease expense ​ $ 50,587 ​ $ 38,189 (a) Includes approximately $5.8 million and $4.9 million of lease impairment charges, $2.8 million and $2.2 million of short-term lease expense, and $5.3 million and $7.6 million of sublease income, for the years ended December 31, 2020 and 2019, respectively. Maturities of lease liabilities as of December 31, 2020 (b) ​ ​ ​ ​ ​ Years Ended December 31, In thousands 2021 ​ $ 38,664 2022 ​ ​ 38,473 2023 ​ 36,648 2024 ​ 35,106 2025 ​ 26,841 Thereafter ​ 227,409 Total ​ 403,141 Less: Interest ​ 168,967 Present value of lease liabilities ​ $ 234,174 (b) Lease payments exclude $0.1 million of legally binding minimum lease payments for leases signed but not yet commenced. The following are the weighted average assumptions used for lease term and discount rate as of December 31, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Remaining lease term 15.4 years 17.4 years ​ Discount rate 5.66 % 6.12 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Other Information: ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ $ 81,636 ​ $ 61,657 Cash paid for amounts included in the measurement of lease liabilities ​ $ 44,978 ​ $ 35,321 ​

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE 14—COMMITMENTS AND CONTINGENCIES Commitments The Company has entered into certain off-balance sheet commitments that require the future purchase of services (“purchase obligations”). Future payments under noncancelable unconditional purchase obligations as of December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of Commitment Expiration Per Period ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Less Than ​ 1-3 ​ 3-5 ​ More Than ​ Amounts ​ ​ 1 Year ​ Years ​ Years ​ 5 Years ​ Committed ​ (In thousands) Purchase obligations ​ $ 45,819 ​ $ 520 ​ $ — ​ $ — ​ $ 46,339 ​ Purchase obligations include (i) remaining payments of $14.4 million related to a two-year cloud computing contract that expires in April 2021, (ii) a remaining payment of $13.2 million related to the purchase of a 50% interest in a corporate aircraft that is expected to be made in 2021, (iii) remaining payment of $10.0 million related to the Company’s allocable share of Old IAC’s cloud computing contract, and (iv) payments of $6.9 million related to advertising commitments to be made in 2021. Old IAC had a $150.0 million three-year cloud computing contract of which Old IAC paid $50.0 million in 2019, and $20.0 million and $80.0 million was assigned to the Company and Match Group, respectively, following the MTCH Separation. The Company paid $10.0 million in 2020 and had a related prepaid asset of $9.8 million at December 31, 2020 included in “Other current assets” on the balance sheet. Contingencies In the ordinary course of business, the Company is a party to various lawsuits. The Company establishes reserves for specific legal matters when it determines that the likelihood of an unfavorable outcome is probable and the loss is reasonably estimable. Management has also identified certain other legal matters where we believe an unfavorable outcome is not probable and, therefore, no reserve is established. Although management currently believes that resolving claims against us, including claims where an unfavorable outcome is reasonably possible, will not have a material impact on the liquidity, results of operations, or financial condition of the Company, these matters are subject to inherent uncertainties and management’s view of these matters may change in the future. The Company also evaluates other contingent matters, including income and non-income tax contingencies, to assess the likelihood of an unfavorable outcome and estimated extent of potential loss. It is possible that an unfavorable outcome of one or more of these lawsuits or other contingencies could have a material impact on the liquidity, results of operations, or financial condition of the Company. See “Note 3—Income Taxes” for additional information related to income tax contingencies. Tinder Optionholder Litigation against IAC and MTCH In August 2018, ten then-current and former employees of Match Group’s Tinder business filed a lawsuit in New York state court against IAC and Match Group. See Sean Rad et al. v. IAC/InterActiveCorp and Match Group, Inc., inter alia In October 2018, the defendants filed a motion to dismiss the complaint on various grounds, including that the 2017 valuation of Tinder by the investment banks was an expert determination any challenge to which is time-barred under applicable law. In June 2019, the court issued a decision and order granting the motion in part but leaving the plaintiffs’ principal claims intact. The defendants appealed from the partial denial of their motion to dismiss, and in October 2019, the Appellate Division, First Department, affirmed the lower court’s decision. After additional appellate motion practice, in May 2020, the Appellate Division reaffirmed the lower court’s decision on different grounds. In June 2020, the defendants filed a motion for leave to appeal that decision to the Court of Appeals; the Appellate Division denied the motion in July 2020. In June 2019, the defendants filed a second motion to dismiss or for other relief based upon certain provisions of the plaintiffs’ agreement with a litigation funding firm; that motion remains pending. From July to November 2019, the defendants filed counterclaims against former Tinder CEO Sean Rad for breach of contract and unjust enrichment based upon his alleged misappropriation and unauthorized destruction of confidential company information, unauthorized recording of conversations with company employees, and breach of his non-solicitation obligations. In January 2020, the parties participated in a mediation that did not result in the resolution of the matter. Document discovery in the case is substantially complete; deposition discovery is nearing completion. In July 2020, the four individuals who earlier had discontinued their claims in the lawsuit commenced arbitration proceedings against IAC and Match Group before the American Arbitration Association in California, asserting the same claims and seeking the same relief as the six remaining plaintiffs in the lawsuit. In September 2020, the defendants filed a motion to stay the trial in the New York lawsuit in favor of the California arbitration; in November 2020, the court denied the motion. In December 2020, the claimants in the California arbitration filed a motion to stay those proceedings in favor of the New York action, in which a trial has been provisionally scheduled for November 2021; in January 2021, the arbitrator denied the motion and provisionally scheduled a hearing on the merits for February 2022. IAC believes that the allegations against it in the New York lawsuit and the California arbitration are without merit and will continue to defend vigorously against them. Pursuant to the Transaction Agreement (as defined in Note 1-Organization -MTCH Separation), Match Group has agreed to indemnify the Company for matters relating to any business of Match Group, including indemnifying the Company for costs related to the matter described above.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	NOTE 15—RELATED PARTY TRANSACTIONS Relationship with Old IAC prior to the MTCH Separation The Company’s statement of operations includes allocations of costs, including stock-based compensation expense, related to Old IAC’s accounting, treasury, legal, tax, corporate support and internal audit functions prior to the MTCH Separation. Old IAC historically allocated costs related to its accounting, treasury, legal, tax, corporate support and internal audit functions that were incurred at the Old IAC legal entity level to its publicly traded subsidiaries, Old MTCH and ANGI Homeservices, for any services provided under the applicable services agreements. The remaining unallocated expenses of Old IAC related to its accounting, treasury, legal, tax, corporate support and internal audit functions were allocated to the Company. Old IAC allocated costs to the Company, inclusive of stock-based compensation expense, in 2020, prior to the MTCH Separation, totaled $85.5 million. Old IAC allocated costs to the Company, inclusive of stock-based compensation expense, totaled $146.0 million and $178.2 million for the years ended December 31, 2019 and 2018, respectively. It is not practicable to determine the actual expenses that would have been incurred for these services had the Company operated as a standalone entity during the periods presented. Management considers the allocation method to be reasonable. The portion of interest income reflected in the statement of operations that is related party in nature was less than $0.1 million in 2020 prior to the MTCH Separation, and $0.4 million and $0.3 million for the years ended December 31, 2019 and 2018, respectively, and is included in “Interest income, net” in the table below. The following table summarizes the components of the net increase in Old IAC’s investment in the Company for the periods prior to the MTCH Separation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months ​ ​ ​ ​ ​ ​ ​ ​ Ended June 30, ​ ​ ​ ​ ​ ​ ​ ​ the date of the ​ ​ ​ ​ ​ ​ ​ ​ MTCH Separation ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Cash transfers (from) to Old IAC related to its centrally managed U.S. treasury management function, acquisitions and cash expenses paid by Old IAC on behalf of the Company, net ​ $ (1,742,854) ​ $ (182,382) ​ $ 215,993 Contribution of buildings to Match Group ​ ​ 34,973 ​ ​ — ​ ​ — Taxes ​ 34,436 ​ (1,874) ​ 1,120 Allocation of costs from Old IAC ​ (12,652) ​ (80,143) ​ (71,977) Interest income, net ​ 102 ​ 420 ​ 325 Net (increase) decrease in Old IAC’s investment in the Company prior to the MTCH Separation ​ $ (1,685,995) ​ $ (263,979) ​ $ 145,461 ​ Notes Receivable—Related Party During 2019, the Company, through two subsidiaries, entered into loan agreements with Old IAC for cash transfers to Old IAC under its centrally managed U.S. treasury function. During the first quarter of 2020, the outstanding balance, which was $55.3 million at December 31, 2019, was repaid. On February 11, 2020, the Company, through a subsidiary, entered into a loan agreement with Old IAC for cash transfers to Old IAC under its centrally managed U.S. treasury function. During the second quarter of 2020, the outstanding balance, which was $27.2 million at March 31, 2020, was repaid. Long-term Debt—Related Party On December 14, 2018, the Company, through a subsidiary, entered into a loan agreement with Old IAC for an amount not to exceed $15.0 million for general working capital purposes in the ordinary course of business. During the first quarter of 2019, the outstanding balance, which was $2.5 million at December 31, 2018, was repaid. IAC and ANGI Old IAC and ANGI, in connection with the Combination, entered into a contribution agreement; an investor rights agreement; a services agreement; a tax sharing agreement; and an employee matters agreement. Upon the MTCH Separation, Old IAC assigned these agreements to the Company. For the year ended December 31, 2020, 0.3 million shares of ANGI Class B common stock were issued to a subsidiary of the Company pursuant to the employee matters agreement as reimbursement for shares of IAC common stock, issued for periods after the MTCH Separation, and Old IAC common stock, issued for periods prior to the MTCH Separation, in connection with the exercise and vesting of IAC and Old IAC equity awards held by ANGI employees. For the years ended December 31, 2019 and 2018, 0.5 million and 0.9 million shares, respectively, of ANGI Class B common stock were issued to a subsidiary of the Company pursuant to the employee matters agreement. On October 10, 2018, Old IAC was issued 5.1 million shares of Class B common stock of ANGI pursuant to the post-closing adjustment provision of the Angie’s List merger agreement. For the years ended December 31, 2020, 2019 and 2018, ANGI was charged $4.8 million, $4.8 million and $5.7 million by IAC, for periods after the MTCH Separation, and Old IAC, for periods prior to the MTCH Separation, for services rendered pursuant to the services agreement. There were no outstanding receivables or payables pursuant to the services agreement as of December 31, 2020 or December 31, 2019. At December 31, 2020 and December 31, 2019, ANGI had outstanding payables of $0.9 million and $0.2 million, respectively, due to the Company pursuant to the tax sharing agreement. There were $3.1 million of refunds made to ANGI pursuant to this agreement during the year ended December 31, 2020. During the first quarter of 2019, $11.4 million was paid to the Company pursuant to this agreement. Additionally, the Company subleases office space from ANGI and was charged rent of $1.8 million and $1.4 million for the years ended December 31, 2020 and 2019, respectively. There were no amounts charged pursuant to subleases for office space between the Company and ANGI for the year ended December 31, 2018. At both December 31, 2020 and 2019, there were outstanding payables of less than $0.1 million due to ANGI pursuant to sublease agreements, which were subsequently paid in full in the first quarter of 2021 and 2020, respectively. IAC and Old MTCH Prior to the MTCH Separation, for the six months ended June 30, 2020, the date of the MTCH Separation, and for the years ended December 31, 2019 and 2018, Old MTCH incurred rent expense of $1.4 million and $5.8 million and $5.2 million respectively, for leasing office space for certain of its businesses at properties owned by the Company. The amounts were paid in full by Old MTCH at the date of the MTCH Separation and at December 31, 2019 and 2018, respectively. After the MTCH Separation, Match Group is no longer a related party. On January 31, 2020, Old IAC contributed two office buildings in Los Angeles to Old MTCH, which are primarily occupied and were previously leased from the Company by Tinder. In connection with this contribution, the Company entered into a lease with Old MTCH for office space, which the Company currently occupies, in one of the buildings and for the six months ended June 30, 2020, the date of the MTCH Separation, the Company paid Old MTCH less than $0.1 million under the lease. Old MTCH issued 1.4 million shares of Old MTCH common stock to Old IAC for the buildings. IAC and Expedia The Company and Expedia each have a 50% ownership interest in two aircrafts that may be used by both companies. In 2019, the Company and Expedia entered into an agreement to jointly acquire a new corporate aircraft for a total expected cost of $72.3 million (including purchase price and related costs), with each company to bear 50% of such expected cost. The Company paid approximately $23 million in 2019 in connection with the purchase agreement, and the respective share of the balance is due upon delivery of the new aircraft, which is expected to occur in the third quarter of 2021. Members of the aircraft flight crews are employed by an entity in which the Company and Expedia each have a 50% ownership interest. The Company and Expedia have agreed to share costs relating to flight crew compensation and benefits pro-rata according to each company’s respective usage of the aircraft, for which they are separately billed by the entity described above. The Company and Expedia are related parties because Mr. Diller serves as Chairman and Senior Executive of both IAC and Expedia. For the years ended December 31, 2020, 2019 and 2018, total payments made to this entity by the Company were not material.

BENEFIT PLANS

BENEFIT PLANS	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
BENEFIT PLANS	NOTE 16—BENEFIT PLANS IAC employees in the United States can elect to participate in a retirement savings program, the IAC/InterActiveCorp Retirement Savings Plan (“the Plan”), that qualifies under Section 401(k) of the Internal Revenue Code. Under the Plan, participating employees may contribute up to 50% of their pre-tax earnings, but not more than statutory limits. Prior to July 2019, the Company contributed an amount equal to 50% of the first 6% of compensation that a participant contributes in each payroll period to the Plan. In June 2019, the Company approved a change to its matching contribution to 100% of the first 10% of an employee’s eligible compensation, subject to IRS limits on the Company’s matching contribution maximum, that a participant contributes to the Plan. This change was phased in beginning July 1, 2019 and was implemented by some but not all of IAC’s subsidiaries participating in the Plan by January 1, 2020. Matching contributions to the Plan for the years ended December 31, 2020, 2019 and 2018 were $20.5 million, $15.4 million and $10.2 million, respectively. Matching contributions are invested in the same manner as each participant’s voluntary contributions in the investment options provided under the Plan. An investment option in the Plan is IAC common stock, but neither participant nor matching contributions are required to be invested in IAC common stock. The increases in matching contributions in both 2020 and 2019 are due primarily to the aforementioned change in the Company’s matching contribution. IAC also has or participates in various benefit plans, principally defined contribution plans, for its international employees. IAC’s contributions to these plans for the years ended December 31, 2020, 2019 and 2018 were $1.0 million, $1.0 million and $0.6 million, respectively.

FINANCIAL STATEMENT DETAILS

FINANCIAL STATEMENT DETAILS	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
FINANCIAL STATEMENT DETAILS	NOTE 17—FINANCIAL STATEMENT DETAILS Cash and Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheet to the total amounts shown in the statement of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 December 31, 2018 December 31, 2017 ​ ​ (In thousands) Cash and cash equivalents ​ $ 3,476,188 ​ $ 839,796 ​ $ 884,975 ​ $ 757,202 Restricted cash included in other current assets ​ 473 ​ 527 ​ 1,441 ​ 2,737 Restricted cash included in other assets ​ 449 ​ 409 ​ 420 ​ — Total cash and cash equivalents and restricted cash as shown on the statement of cash flows ​ $ 3,477,110 ​ $ 840,732 ​ $ 886,836 ​ $ 759,939 ​ Restricted cash included in other current assets at December 31, 2020 primarily consists of cash received from customers at ANGI through their Handy platform, representing funds collected for payments to service providers, which were not settled as of the period end. Restricted cash at December 31, 2019 primarily consists of a deposit related to corporate credit cards. Restricted cash at December 31, 2018 primarily consists of a cash collateralized letter of credit and a deposit related to corporate credit cards. Restricted cash at December 31, 2017 primarily supports a letter of credit to a supplier, which was released to the Company in the second quarter of 2018. Restricted cash included in other non-current assets for all periods presented consists of deposits related to leases. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Other current assets: ​ ​ Capitalized costs to obtain a contract with a customer ​ $ 61,514 ​ $ 43,069 Prepaid expenses ​ 50,123 ​ 41,934 Capitalized downloadable search toolbar costs, net ​ 12,730 ​ 21,985 Other ​ 23,263 ​ 45,346 Other current assets ​ $ 147,630 ​ $ 152,334 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Building, capitalized software, leasehold improvements and equipment ​ ​ Buildings and leasehold improvements ​ $ 198,778 ​ $ 242,882 Capitalized software and computer equipment ​ 149,789 ​ 124,523 Furniture and other equipment ​ 84,161 ​ 84,640 Land ​ — ​ 11,591 Projects in progress ​ 53,635 ​ 43,576 Building, capitalized software, leasehold improvements and equipment ​ 486,363 ​ 507,212 Accumulated depreciation and amortization ​ (208,112) ​ (201,798) Building, capitalized software, leasehold improvements and equipment, net ​ $ 278,251 ​ $ 305,414 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Accrued expenses and other current liabilities: ​ ​ Accrued employee compensation and benefits ​ $ 126,161 ​ $ 105,960 Accrued advertising expense ​ 62,854 ​ 59,269 Accrued revenue share ​ 38,710 ​ 30,574 Other ​ 155,837 ​ 124,670 Accrued expenses and other current liabilities ​ $ 383,562 ​ $ 320,473 ​ Other (expense) income, net ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Impairments related to COVID-19 (a) ​ $ (59,001) ​ $ — ​ $ — Realized gains related to the sale of investments ​ 10,661 ​ 2,327 ​ 589 Realized gains related to the sale of the investment in Pinterest ​ — ​ 20,486 ​ 26,777 Upward adjustments to the carrying value of equity securities without readily determinable fair values (b) ​ — ​ 18,505 ​ 128,901 Interest income ​ 7,189 ​ 15,164 ​ 9,125 Realized gains (losses) related to the sale of business (c) ​ 1,061 ​ (8,239) ​ 121,230 Unrealized reduction in the estimated fair value of a warrant ​ (1,213) ​ (9,123) ​ — Mark-to-market loss on an indemnification claim related to the Handy acquisition ​ (181) ​ (1,779) ​ — Other ​ (984) ​ (3,294) ​ (3,827) Other (expense) income, net ​ $ (42,468) ​ $ 34,047 ​ $ 282,795 (a) Includes $51.5 million in impairments related to investments in equity securities without readily determinable fair values and $7.5 million in impairments of a note receivable and a warrant related to certain investees in the year ended December 31, 2020. (b) Includes a $128.8 million unrealized gain to adjust the remaining interest in Pinterest to fair value in accordance with ASU No. 2016-02 in the year ended December 31, 2018. (c) Includes a realized loss on the sale of Vimeo’s hardware business, which was sold in the first quarter of 2019, and gains related to the sales of Dictionary.com, Electus, Felix and CityGrid in the year ended December 31, 2018. Supplemental Disclosure of Cash Flow Information: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Cash paid (received) during the year for: ​ ​ ​ Interest ​ $ 6,524 ​ $ 10,042 ​ $ 13,108 Income tax payments ​ $ 6,876 ​ $ 4,861 ​ $ 4,084 Income tax refunds ​ $ (2,080) ​ $ (3,048) ​ $ (30,320) ​ Supplemental Disclosure of Non-Cash Transactions: The Company recorded an acquisition-related contingent consideration liability of $25.5 million during the year ended December 31, 2018, in connection with an acquisition. There were no acquisition-related contingent consideration liabilities recorded for the years ended December 31, 2020 and 2019. See “Note 6—Financial Instruments and Fair Value Measurements” for additional information on contingent consideration arrangements. On October 19, 2018, ANGI issued 8.6 million shares of its Class A common stock valued at $165.8 million in connection with the acquisition of Handy.

QUARTERLY RESULTS (UNAUDITED)

QUARTERLY RESULTS (UNAUDITED)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY RESULTS (UNAUDITED)	NOTE 18—QUARTERLY RESULTS (UNAUDITED) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarter Ended Quarter Ended Quarter Ended Quarter Ended ​ ​ ​ March 31 (a)(e) ​ June 30 (b)(e) ​ September 30 (c)(e) ​ December 31 (d)(e) ​ ​ ​ (In thousands, except per share data) Year Ended December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenue ​ ​ $ 684,124 ​ $ 726,361 ​ $ 788,377 ​ $ 848,819 Cost of revenue ​ ​ $ 179,327 ​ $ 178,639 ​ $ 207,643 ​ $ 249,122 Operating loss ​ ​ $ (312,338) ​ $ (107,019) ​ $ (128,626) ​ $ (24,366) Net (loss) earnings ​ ​ $ (330,571) ​ $ (94,064) ​ $ 185,861 ​ $ 507,360 Net (loss) earnings attributable to IAC shareholders ​ ​ $ (328,199) ​ $ (96,117) ​ $ 184,917 ​ $ 509,125 Per share information attributable to IAC shareholders: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic (loss) earnings per share (f)(g) ​ ​ $ (3.86) ​ $ (1.13) ​ $ 2.17 ​ $ 5.96 Diluted (loss) earnings per share (f)(g) ​ ​ $ (3.86) ​ $ (1.13) ​ $ 2.04 ​ $ 5.59 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarter Ended Quarter Ended Quarter Ended Quarter Ended ​ ​ March 31 (e) ​ June 30 (e) ​ September 30 (e) ​ December 31 (e) ​ ​ (In thousands, except per share data) Year Ended December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ Revenue ​ $ 641,220 ​ $ 688,685 ​ $ 705,382 ​ $ 670,514 Cost of revenue ​ $ 139,848 ​ $ 149,725 ​ $ 158,161 ​ $ 152,506 Operating (loss) income ​ $ (34,183) ​ $ (13,770) ​ $ 13,912 ​ $ (16,408) Net (loss) earnings ​ $ (13,673) ​ $ 22,021 ​ $ 18,378 ​ $ 5,457 Net (loss) earnings attributable to IAC shareholders ​ $ (14,247) ​ $ 13,789 ​ $ 16,466 ​ $ 6,887 Per share information attributable to IAC shareholders: ​ ​ ​ ​ Basic (loss) earnings per share (f)(g) ​ $ (0.17) ​ $ 0.16 ​ $ 0.19 ​ $ 0.08 Diluted (loss) earnings per share (f)(g) ​ $ (0.17) ​ $ 0.16 ​ $ 0.19 ​ $ 0.08 (a) The first quarter of 2020 includes: i. as a result of the effects of COVID-19: ● an after-tax $208.9 million impairment related to the goodwill of the Desktop reporting unit; ● an after-tax $16.4 million impairment related to certain indefinite-lived intangible assets of the Desktop reporting unit; ● an after-tax $51.5 million impairment of certain equity securities without readily determinable fair values; and ● an after-tax $7.5 million impairment of a note receivable and a warrant related to certain investee. (b) The second quarter includes: i. after-tax stock-based compensation expense of $40.7 million related to the modification of previously issued equity awards as a result of the MTCH Separation; and an ii. after-tax unrealized loss of $24.7 million related to IAC’s investment in MGM. (c) The third quarter of 2020 includes: i. an after-tax $53.2 million impairment related to the goodwill of the Desktop reporting unit; ii. an after-tax $8.3 million impairment of intangible assets of the Desktop reporting unit; and an iii. after-tax unrealized gain of $227.7 million related to IAC’s investment in MGM. (d) The fourth quarter of 2020 includes after-tax unrealized gain of $439.6 million related to IAC’s investment in MGM. (e) The first, second, third and fourth quarters of 2020 include after-tax stock-based compensation expense of $8.9 million, $2.7 million, $4.1 million and $1.5 million, respectively, related to the modification of previously issued HomeAdvisor equity awards and previously issued Angie’s List equity awards, both of which were converted into ANGI Homeservices’ equity awards in the Combination. The first, second, third and fourth quarters of 2019 include after-tax stock-based compensation expense of $7.4 million, $6.3 million, $5.7 million, and $5.7 million, respectively, related to this modification. (f) Quarterly per share amounts may not add to the related annual per share amount because of differences in the average common shares outstanding during each period. (g) The Company computed basic and diluted earnings per share for periods prior to the MTCH Separation using the shares issued on June 30, 2020 in connection with the MTCH Separation.

SUBSEQUENT EVENTS SUBSEQUENT EV

SUBSEQUENT EVENTS SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE 19—SUBSEQUENT EVENTS In January 2021, Vimeo raised $300 million of equity capital via the sale of 6.2 million shares of Vimeo Class A voting common stock for $200 million, or $32.41 per share, at a $5.2 billion pre-money valuation, and 2.8 million shares of Vimeo Class A voting common stock for $100 million, or $35.35 per share, at a $5.7 billion pre-money valuation. Following the sale, IAC holds On February 12, 2021, Vimeo, Inc. entered into a five-year $100 million revolving credit facility (the “Vimeo Credit Facility”), which is secured by substantially all of its assets, subject to certain exceptions. Borrowings under the Vimeo Credit Facility bear interest, at Vimeo’s option, at either a base rate or LIBOR, in each case plus an applicable margin, which is determined by reference to a pricing grid based on Vimeo’s consolidated net leverage ratio. At closing, there were no borrowings under the Vimeo Credit Facility.

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS	Schedule II IAC/INTERACTIVECORP AND SUBSIDIARIES VALUATION AND QUALIFYING ACCOUNTS ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Beginning ​ Charges to ​ Charges to ​ ​ ​ ​ Balance at Description ​ of Period ​ Earnings ​ Other Accounts ​ Deductions ​ End of Period ​ (In thousands) 2020 ​ ​ ​ ​ ​ Allowance for credit losses ​ $ 20,257 ​ $ 80,765 (a) $ (52) ​ $ (73,316) (c) $ 27,654 Revenue reserves ​ ​ 3,891 ​ ​ 110,796 (b) ​ — ​ ​ (112,625) (d) ​ 2,062 Deferred tax valuation allowance ​ ​ 92,990 ​ 11,623 (e) 9,071 (f) — ​ 113,684 Other reserves ​ ​ 5,060 ​ ​ ​ ​ 8,054 2019 ​ ​ ​ ​ ​ Allowance for credit losses ​ $ 16,344 ​ $ 65,723 (a) $ 247 ​ $ (62,057) (c) $ 20,257 Revenue reserves ​ ​ 1,792 ​ ​ 114,005 (b) ​ (2) ​ ​ (111,904) (d) ​ 3,891 Deferred tax valuation allowance ​ 86,778 ​ 7,813 (g) (1,601) (f) — ​ 92,990 Other reserves ​ 4,726 ​ ​ ​ ​ ​ ​ ​ ​ 5,060 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses ​ $ 9,075 ​ $ 48,362 (a) $ (451) ​ $ (40,642) (c) $ 16,344 Revenue reserves ​ ​ 1,635 ​ ​ 87,803 (b) ​ (5) ​ ​ (87,641) (d) ​ 1,792 Deferred tax valuation allowance ​ 91,040 ​ (2,056) (h) (2,206) (f) — ​ 86,778 Other reserves ​ — ​ ​ ​ ​ ​ ​ ​ ​ 4,726 (a) Additions to the allowance for credit losses are charged to expense. (b) Additions to the revenue reserves are charged against revenue. (c) Write-off of fully reserved accounts receivable. (d) Amount is primarily related to write-off of revenue reserve at ANGI primarily related to credits granted to service professionals. (e) Amount is primarily related to impairments of certain equity securities without readily determinable fair values. (f) Amount is primarily related to currency translation adjustments on foreign NOLs. (g) Amount is primarily related to an increase in foreign NOLs partially offset by a net decrease in unbenefited capital losses. (h) Amount is primarily related to an expired tax credit.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Combination	Basis of Presentation and Combination As used herein, “IAC,” “the Company,” “we,” “our” or “us” and similar terms refer to IAC/InterActiveCorp and its subsidiaries (unless the context requires otherwise). The Company prepares its consolidated and combined financial statements (collectively referred to herein as “financial statements”) in accordance with U.S. generally accepted accounting principles (“GAAP”). The Company’s financial statements were prepared on a consolidated basis beginning June 30, 2020 and on a combined basis for periods prior thereto. The difference in presentation is due to the fact that the final steps of the legal reorganization, including the contribution of all the entities that comprise the Company prior to the MTCH Separation, were not completed until June 30, 2020. The preparation of the financial statements on a combined basis for periods prior to June 30, 2020 allows for the financial statements to be presented on a consistent basis for all periods presented. The historical combined financial statements of the Company have been derived from the historical accounting records of Old IAC. The combined financial statements reflect the historical financial position, results of operations and cash flows of the entities comprising the Company since their respective dates of acquisition by Old IAC and the allocation to the Company of certain Old IAC corporate expenses based on the historical accounting records of Old IAC through June 30, 2020. The consolidated financial statements include the accounts of the Company, all entities that are wholly-owned by the Company and all entities in which the Company has a controlling financial interest. For the purpose of the combined financial statements, income taxes have been computed as if the entities comprising the Company filed tax returns on a standalone, separate basis for periods prior to the MTCH Separation. All intercompany transactions and balances between and among the Company and its subsidiaries have been eliminated. All intercompany transactions between (i) the Company and (ii) Old IAC and its subsidiaries for periods prior to the MTCH Separation are considered to be effectively settled for cash at the time the transaction was recorded. The total net effect of the settlement of these intercompany transactions is reflected in the statement of cash flows as a financing activity and in the balance sheet as “Invested capital.” In management’s opinion, the assumptions underlying the historical financial statements of the Company, including the basis on which the expenses have been allocated from Old IAC, are reasonable. However, the allocations may not reflect the expenses that the Company would have incurred as an independent, stand-alone company for the periods presented. COVID-19 Update and Impairments The impact on the Company from the COVID-19 outbreak, which has been declared a “pandemic” by the World Health Organization, has been varied. The extent to which developments related to the COVID-19 outbreak and measures designed to curb its spread continue to impact the Company’s business, financial condition and results of operations will depend on future developments, all of which are highly uncertain and many of which are beyond the Company’s control, including the speed of contagion, the development and implementation of effective preventative measures and possible treatments, the scope of governmental and other restrictions on travel, discretionary services and other activity, and public reactions to these developments. For example, these developments and measures have resulted in rapid and adverse changes to the operating environment in which we do business, as well as significant uncertainty concerning the near and long term economic ramifications of the COVID-19 outbreak, which have adversely impacted our ability to forecast our results and respond in a timely and effective manner to trends related to the COVID-19 outbreak. The longer the global outbreak and measures designed to curb the spread of the virus continue to adversely affect levels of consumer confidence, discretionary spending and the willingness of consumers to interact with other consumers, vendors and service providers face-to-face (and in turn, adversely affect demand for the Company’s various products and services), the greater the adverse impact is likely to be on the Company’s business, financial condition and results of operations and the more limited will be the Company’s ability to try and make up for delayed or lost revenues. When COVID-19 first impacted the Company’s ANGI Homeservices business in the spring of 2020, ANGI Homeservices experienced a decline in demand for service requests, driven primarily by decreases in demand in certain categories of jobs (particularly discretionary indoor projects). Toward the end of the spring of 2020, ANGI Homeservices experienced a rebound in service requests, exceeding pre-COVID-19 growth levels, driven by increased demand from homeowners who spent more time at home due to measures taken to reduce the spread of COVID-19. ANGI Homeservices continued to experience strong demand for home services in the second half of 2020. However, many service professionals’ businesses have been adversely impacted by labor and material constraints and many service professionals have limited capacity to take on new business, which has negatively impacted ANGI Homeservices’ ability to monetize this increased level of service requests. Vimeo has seen strong revenue growth as the demand for communication via video has increased due to the pandemic. The Search segment has experienced a decline in revenue due, in part, to the decrease in advertising rates due to the impact of COVID-19, which decrease in rates was more significant earlier in the year. In the quarter ended March 31, 2020, the Company determined that the effects of COVID-19 were an indicator of possible impairment for certain of its assets and identified the following impairments: ● a $ 212.0 million impairment related to the goodwill of the Desktop reporting unit; ● a $21.4 million impairment related to certain indefinite-lived intangible assets of the Desktop reporting unit; ● a $51.5 million impairment of certain equity securities without readily determinable fair values; and ● a $7.5 million impairment of a note receivable and a warrant related to certain investees. In the quarter ended September 30, 2020, the Company reassessed the fair values of the Desktop reporting unit and the related indefinite-lived intangible assets and recorded impairments equal to the remaining carrying value of the goodwill of $53.2 million and $10.8 million related to the intangible assets. The reduction in the Company’s fair value estimates of the Desktop business in the first and third quarters of 2020 was primarily due to lower consumer queries, increasing challenges in monetization and the reduced ability to market profitably due to browser policy changes implemented by Google and other browsers. The effects of COVID-19 on monetization were an additional factor. Refer to “Certain Risks and Concentrations—Services Agreement with Google” for additional information. There were no additional impairments identified during the year ended December 31, 2020. In addition, the United States, which represents 80% of the Company’s revenue for the year ended December 31, 2020, experienced a significant resurgence of the coronavirus and with record levels of COVID-19 infections being reported during the fourth quarter of 2020 and continuing into the first quarter of 2021. Europe, which is the second largest market for the Company’s products and services, has also seen a dramatic resurgence in COVID-19. This resurgence and the measures designed to curb its spread could materially and adversely affect our business, financial condition and results of operations.
Accounting Estimates	Accounting Estimates Management of the Company is required to make certain estimates, judgments and assumptions during the preparation of its financial statements in accordance with GAAP. These estimates, judgments and assumptions impact the reported amounts of assets, liabilities, revenue and expenses and the related disclosure of assets and liabilities. Actual results could differ from these estimates. On an ongoing basis, the Company evaluates its estimates, judgments and assumptions, including those related to: the fair values of cash equivalents and marketable debt and equity securities; the carrying value of accounts receivable, including the determination of the allowance for credit losses; the determination of revenue reserves; the determination of the customer relationship period for certain costs to obtain a contract with a customer; the carrying value of right-of-use assets (“ROU assets”); the useful lives and recoverability of building, capitalized software, leasehold improvements and equipment and definite-lived intangible assets; the recoverability of goodwill and indefinite-lived intangible assets; the fair value of equity securities without readily determinable fair values; contingencies; the fair value of acquisition-related contingent consideration arrangements; unrecognized tax benefits; the valuation allowance for deferred income tax assets; and the fair value of and forfeiture rates for stock-based awards, among others. The Company bases its estimates, judgments and assumptions on historical experience, its forecasts and budgets and other factors that the Company considers relevant.
Accounting for Investments in Equity Securities	Accounting for Investments in Equity Securities Investments in equity securities, other than those of the Company’s consolidated subsidiaries and those accounted for under the equity method, if applicable, are accounted for at fair value or under the measurement alternative of Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , with any changes to fair value recognized within other (expense) income, net each reporting period. Under the measurement alternative, equity investments without readily determinable fair values are carried at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar securities of the same issuer; value is generally determined based on a market approach as of the transaction date. A security will be considered identical or similar if it has identical or similar rights to the equity securities held by the Company. The Company reviews its investments in equity securities without readily determinable fair values for impairment each reporting period when there are qualitative factors or events that indicate possible impairment. Factors the Company considers in making this determination include negative changes in industry and market conditions, financial performance, business prospects, and other relevant events and factors. When indicators of impairment exist, the Company prepares quantitative assessments of the fair value of its investments in equity securities, which require judgment and the use of estimates. When the Company’s assessment indicates that the fair value of the investment is below its carrying value, the Company writes down the investment to its fair value and records the corresponding charge within other (expense) income, net. See “Note 6 - Financial Instruments and Fair Value Measurements” for additional information on the impairments of certain equity securities without readily determinable fair values recorded during the year ended December 31, 2020. In the event the Company has investments in the common stock or in-substance common stock of entities in which the Company has the ability to exercise significant influence over the operating and financial matters of the investee, but does not have a controlling financial interest, are accounted for using the equity method and are included in “Long-term investments” in the accompanying balance sheet. At December 31, 2020, the Company has one investment accounted for using the equity method. At December 31, 2019, the Company did not have any investments accounted for using the equity method.
Revenue Recognition	Revenue Recognition The Company accounts for a contract with a customer when it has approval and commitment from all parties, the rights of the parties and payment terms are identified, the contract has commercial substance and collectability of consideration is probable. Revenue is recognized when control of the promised services or goods is transferred to our customers and in an amount that reflects the consideration the Company expects to be entitled to in exchange for those services or goods. The Company adopted ASU No. 2014-09, Revenue from Contracts with Customers, effective January 1, 2018 using the modified retrospective transition method for open contracts as of the date of initial application. The cumulative effect to the Company’s retained earnings at January 1, 2018 was an increase of $40.3 million, of which $3.4 million was related to the noncontrolling interest in ANGI; the adjustment to retained earnings was principally related to the Company’s ANGI segment and the Desktop business. ● Within ANGI, the effect of the adoption of ASU No. 2014-09 was that commissions paid to employees pursuant to certain sales incentive programs, which represent the incremental direct costs of obtaining a service professional contract, are now capitalized and amortized over the estimated life of a service professional (also referred to as the estimated customer relationship period). These costs were expensed as incurred prior to January 1, 2018. The cumulative effect of the adoption of ASU No. 2014-09 was the establishment of a current and non-current asset for capitalized sales commissions of $29.7 million and $4.2 million, respectively, and a related deferred tax liability of $ 8.0 million, resulting in a net increase to retained earnings of $25.9 million on January 1, 2018. ● Within the Desktop business, the primary effect of the adoption of ASU No. 2014-09 was to accelerate the recognition of the portion of the revenue of certain desktop applications sold by SlimWare that qualify as functional intellectual property (“functional IP”) under ASU No. 2014-09. This revenue was previously deferred and recognized over the applicable subscription term. The cumulative effect of the adoption of ASU No. 2014-09 for SlimWare was a reduction in deferred revenue of $20.3 million and the establishment of a deferred tax liability of $4.9 million, resulting in a net increase to retained earnings of $15.5 million on January 1, 2018. The Company’s disaggregated revenue disclosures are presented in “Note 12—Segment Information.” Transaction Price The objective of determining the transaction price is to estimate the amount of consideration the Company is due in exchange for its services or goods, including amounts that are variable. The Company determines the total transaction price, including an estimate of any variable consideration, at contract inception and reassesses this estimate each reporting period. The Company excludes from the measurement of transaction price all taxes assessed by governmental authorities that are both (i) imposed on and concurrent with a specific revenue-producing transaction and (ii) collected from customers. Accordingly, such tax amounts are not included as a component of revenue or cost of revenue. For contracts that have an original duration of one year or less, the Company uses the practical expedient available under ASU No. 2014-09, applicable to such contracts and does not consider the time value of money. Arrangements with Multiple Performance Obligations The Company’s contracts with customers may include multiple performance obligations. For such arrangements, the Company allocates revenue to each performance obligation based on its relative standalone selling price. The Company generally determines standalone selling prices based on the prices charged to customers, which are directly observable or based on an estimate if not directly observable. For our multiple performance obligation arrangements that include functional intellectual property (“IP”), which comprise the downloadable apps and software of the Desktop business, the Company uses a residual approach to determine standalone selling prices for the functional IP. Assets Recognized from the Costs to Obtain a Contract with a Customer The Company has determined that certain costs, primarily commissions paid to employees pursuant to certain sales incentive programs and mobile app store fees, meet the requirements to be capitalized as a cost of obtaining a contract. Commissions paid to employees pursuant to certain sales incentive programs are amortized over the estimated customer relationship period. The Company calculates the estimated customer relationship period as the average customer life, which is based on historical data. When customer renewals are expected and the renewal commission is not commensurate with the initial commission, the average customer life includes renewal periods. For sales incentive programs where the customer relationship period is one year or less, the Company has elected the practical expedient to expense the costs as incurred. The Company generally capitalizes and amortizes mobile app store fees over the term of the applicable subscription. During the years ended December 31, 2020, 2019 and 2018, the Company recognized expense of $109.0 million, $99.8 million and $70.6 million related to the amortization of these costs. The current contract asset balances are $61.5 million, $43.1 million and $40.6 million at December 31, 2020, 2019 and 2018, respectively. The non-current contract asset balances are $9.3 million, $6.2 million and $4.5 million at December 31, 2020, 2019 and 2018, respectively. The current and non-current contract assets are included in “Other current assets” and “Other non-current assets,” respectively, in the accompanying balance sheet. Performance Obligations As permitted under the practical expedient available under ASU No. 2014-09, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less, (ii) contracts with variable consideration that is allocated entirely to unsatisfied performance obligations or to a wholly unsatisfied promise accounted for under the series guidance, and (iii) contracts for which the Company recognizes revenue at the amount which it has the right to invoice for services performed. ANGI Homeservices ANGI revenue is primarily derived from consumer connection revenue, which comprises fees paid by HomeAdvisor service professionals for consumer matches (regardless of whether the service professional ultimately provides the requested service) and revenue from completed jobs sourced through the HomeAdvisor and Handy platforms. Consumer connection revenue varies based upon several factors, including the service requested, product experience offered and geographic location of service. The Company’s consumer connection revenue is generated and recognized when an in-network service professional is delivered a consumer match or when a job sourced through the HomeAdvisor and Handy platforms are completed. Consumer connection revenue is generally billed one week following a consumer match, with payment due upon receipt of invoice or collected when a consumer schedules a job through the HomeAdvisor and Handy platforms. The Company maintains revenue reserves for potential credits for services provided by Handy service professionals to consumers. ANGI revenue is also derived from (i) sales of time-based website, mobile and call center advertising to service professionals, (ii) HomeAdvisor service professional membership subscription fees, (iii) membership subscription fees from consumers and (iv) service warranty subscription and other services. Angie’s List service professionals generally pay for advertisements in advance on a monthly or annual basis at the option of the service professional, with the average advertising contract term being approximately one year . Angie’s List website, mobile and call center advertising revenue is recognized ratably over the contract term. Revenue from the sale of advertising in the Angie’s List Magazine is recognized in the period in which the publication is distributed. Service professional membership subscription revenue is initially deferred and is recognized using the straight-line method over the applicable subscription period, which is typically one year. Angie’s List prepaid consumer membership subscription fees are recognized as revenue using the straight-line method over the term of the applicable subscription period, which is typically one year. Prior to January 1, 2020, ANGI’s Handy business recorded revenue on a net basis. Effective January 1, 2020, ANGI modified the Handy terms and conditions so that Handy, rather than the service professional, has the contractual relationship with the consumer to deliver the service and Handy, rather than the consumer, has the contractual relationship with the service professional. Consumers request services and pay for such services directly through the Handy platform and then Handy fulfills the request with independently established home services providers engaged in a trade, occupation and/or business that customarily provides such services. This change in contractual terms requires gross revenue accounting treatment effective January 1, 2020. Also, in the case of certain tasks, HomeAdvisor provides a pre-priced product offering, pursuant to which consumers can request services through a HomeAdvisor platform and pay HomeAdvisor for the services directly. HomeAdvisor then fulfills the request with independently established home services providers engaged in a trade, occupation and/or business that customarily provides such services. Revenue from HomeAdvisor’s pre-priced product offering is also recorded on a gross basis effective January 1, 2020. The change to gross revenue reporting for Handy and HomeAdvisor’s pre-priced product offering, effective January 1, 2020, resulted in an increase in revenue of $73.8 million during the year ended December 31, 2020. Vimeo Vimeo revenue is derived primarily from annual and monthly SaaS subscription fees paid by subscribers for self-serve and enterprise subscription plans. Subscription revenue is recognized over the terms of the applicable subscription period, which range from one month to three years . The most common subscription is an annual subscription. Dotdash Dotdash revenue consists principally of display advertising revenue and performance marketing revenue. Display advertising revenue is generated primarily through digital display advertisements sold directly by our sales team and through programmatic advertising networks. Performance marketing revenue includes affiliate commerce and performance marketing commissions. Affiliate commerce commission revenue is generated when Dotdash refers users to commerce partner websites resulting in a purchase or transaction. Performance marketing commissions are generated on a cost-per-click or cost-per-action basis. Search Ask Media Group revenue consists principally of advertising revenue generated principally through the display of paid listings in response to search queries, as well as from display advertisements appearing alongside content on its various websites and, to a lesser extent, affiliate commerce commission revenue. Paid listings are advertisements displayed on search results pages that generally contain a link to advertiser websites. The majority of the paid listings displayed by Ask Media Group is supplied to us by Google Inc. (“Google”) pursuant to our services agreement with Google. Pursuant to this agreement, Ask Media Group businesses transmit search queries to Google, which in turn transmits a set of relevant and responsive paid listings back to these businesses for display in search results. This ad-serving process occurs independently of, but concurrently with, the generation of algorithmic search results for the same search queries. Google paid listings are displayed separately from algorithmic search results and are identified as sponsored listings on search results pages. Paid listings are priced on a price per click basis and when a user submits a search query through an Ask Media Group business and then clicks on a Google paid listing displayed in response to the query, Google bills the advertiser that purchased the paid listing and shares a portion of the fee charged to the advertiser with the Ask Media Group business. The Company recognizes paid listing revenue from Google when it delivers the user’s click. In cases where the user’s click is generated due to the efforts of a third-party distributor, we recognize the amount due from Google as revenue and record a revenue share or other payment obligation to the third-party distributor as traffic acquisition costs. Revenue from display advertising is generated through advertisements sold through programmatic advertising networks. Affiliate commerce commission revenue is generated when an Ask Media Group property refers users to commerce partner websites resulting in a purchase or transaction. Desktop revenue largely consists of advertising revenue generated principally through the display of paid listings in response to search queries. The majority of the paid listings displayed are supplied to us by Google in the manner, and pursuant to the services agreement with Google, described above. To a lesser extent, Desktop revenue also includes fees paid by subscribers for downloadable desktop applications as well as display advertisements. Fees related to subscription downloadable desktop applications are generally recognized over the term of the applicable subscription period, which is primarily one or two years . Fees related to display advertisements are recognized when an advertisement is displayed. Emerging & Other Mosaic Group revenue consists primarily of fees paid by subscribers for downloadable mobile applications distributed through the Apple App Store and Google Play Store and directly from consumers, as well as display advertisements. Fees related to subscription downloadable mobile applications are generally recognized either over the term of the subscription period, which is up to one year, for those applications that must be connected to our servers to function, or at the time of the sale when the software license is delivered. Fees related to display advertisements are recognized when an advertisement is displayed. Care.com generates revenue primarily through subscription fees from families and caregivers for its suite of products and services, as well as through annual contracts with corporate employers who provide access to Care.com’s suite of products and services as an employee benefit and through contracts with businesses that recruit employees through its platform. Bluecrew revenue consists of service revenue, which is generated through staffing workers and recognized as control of the promised services is transferred to our customers. The Daily Beast revenue consists of advertising revenue, which is generated primarily through display advertisements (sold directly and through programmatic ad sales), and to a lesser extent, affiliate commerce commission revenue. NurseFly revenue consists of subscription revenue, which is generated through recruiting agencies that seek access to qualified healthcare professionals and is recognized at the earlier of the full delivery of the promised services or the length of the subscription period. Revenue of IAC Films and College Humor Media, which was sold in the first quarter of 2020, is generated primarily through media production and distribution and advertising. Production revenue is recognized when control is transferred to the customer to broadcast or exhibit, and advertising revenue is recognized when an advertisement is displayed or over the advertising period. Accounts Receivables, Net of the Allowance for Credit Losses and Revenue Reserves Accounts receivable include amounts billed and currently due from customers. The allowance for credit losses is based upon a number of factors, including the length of time accounts receivable are past due, the Company’s previous loss history, the specific customer’s ability to pay its obligation and any other forward-looking data regarding customers’ ability to pay which may be available. The time between the Company issuance of an invoice and payment due date is not significant; customer payments that are not collected in advance of the transfer of promised services or goods are generally due no later than 30 days from invoice date. The Company also maintains allowances to reserve for potential credits issued to consumers or other revenue adjustments. The amounts of these reserves are based primarily upon historical experience. Credit Losses and Revenue Reserve The following table presents the changes in the allowance for credit losses for the year ended December 31, 2020: ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ (In thousands) Balance at January 1 ​ $ 20,257 Current period provision for credit losses ​ 80,765 Write-offs charged against the allowance ​ (75,815) Recoveries collected ​ 2,447 Balance at December 31 ​ $ 27,654 ​ The revenue reserve was $2.1 million and $3.9 million at December 31, 2020 and 2019, respectively. The total allowance for credit losses and revenue reserve was $29.7 million and $24.1 million as of December 31, 2020 and 2019, respectively. Deferred Revenue Deferred revenue consists of payments that are received or are contractually due in advance of the Company’s performance. The Company’s deferred revenue is reported on a contract by contract basis at the end of each reporting period. The Company classifies deferred revenue as current when the term of the applicable subscription period or expected completion of its performance obligation is one year or less. The current and non-current deferred revenue balances are $178.6 million and $1.3 million, respectively, at December 31, 2019 and $150.1 million and $1.7 million, respectively, at December 31, 2018. During the year ended December 31, 2019, the Company recognized $146.5 million of revenue that was included in the deferred revenue balance as of December 31, 2018. During the year ended December 31, 2020, the Company recognized $170.7 million of revenue that was included in the deferred revenue balance as of December 31, 2019. The current and non-current deferred revenue balances are $275.1 million and $1.5 million, respectively, at December 31, 2020. Non-current deferred revenue is included in “Other long-term liabilities” in the accompanying balance sheet.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash and short-term investments, with maturities of less than 91 days from the date of purchase. Domestically, cash equivalents primarily consist of AAA rated government money market funds, treasury discount notes and time deposits. Internationally, cash equivalents primarily consist of AAA rated government money market funds and time deposits.
Investments in Debt Securities	Investments in Debt Securities The Company invests in marketable debt securities with active secondary or resale markets to ensure portfolio liquidity to fund current operations or satisfy other cash requirements as needed. Marketable debt securities are adjusted to fair value each quarter, and the unrealized gains and losses, net of tax, are included in accumulated other comprehensive income (loss) as a separate component of shareholders’ equity. The specific-identification method is used to determine the cost of debt securities sold and the amount of unrealized gains and losses reclassified out of accumulated other comprehensive income (loss) into earnings. The Company also invests in non-marketable debt securities as part of its investment strategy. We review our debt securities for impairment each reporting period. The Company recognizes an unrealized loss on debt securities in net earnings when the impairment is determined to be other-than-temporary. Factors we consider in making such determination include the duration, severity and reason for the decline in value and the potential recovery and our intent to sell the debt security. We also consider whether we will be required to sell the security before recovery of its amortized cost basis and whether the amortized cost basis cannot be recovered because of credit losses. If an impairment is considered to be other-than-temporary, the debt security will be written down to its fair value and the loss will be recognized within other (expense) income, net. At December 31, 2020 marketable debt securities consist of treasury discount notes. There were no marketable debt securities at December 31, 2019.
Certain Risks and Concentration Services Agreement with Google (the "Services Agreement")	Certain Risks and Concentrations—Services Agreement with Google (the “Services Agreement”) A meaningful portion of the Company’s revenue (and a substantial portion of IAC’s net cash from operations that it can freely access) is attributable to the Services Agreement. In addition, the Company earns certain other advertising revenue from Google that is not attributable to the Services Agreement. For the years ended December 31, 2020, 2019 and 2018, total revenue earned from Google was $556.4 million, $733.5 million and $825.2 million, respectively, representing 18% , 27% , and 33% , respectively, of the Company’s total revenue. The related accounts receivable totaled $61.9 million and $53.0 million at December 31, 2020 and 2019, respectively. The total revenue earned from the Services Agreement for the years ended December 31, 2020, 2019 and 2018, was $498.3 million, $677.0 million and $765.6 million, respectively, representing 16% , 25% and 30% , respectively, of the Company’s total revenue. The revenue attributable to the Services Agreement is earned by the Desktop business and Ask Media Group, both within the Search segment. For the years ended December 31, 2020, 2019 and 2018, revenue earned from the Services Agreement was $153.5 million, $291.1 million and $426.5 million, respectively, within the Desktop business and $344.8 million, $385.9 million and $339.0 million, respectively, within Ask Media Group. The Services Agreement expires on March 31, 2023; provided that during each September, either party may, after discussion with the other party, terminate the Services Agreement, effective on September 30 of the year following the year such notice is given. Neither party gave notice to the other party to terminate the Services Agreement pursuant to this provision in September 2020. The Services Agreement requires that the Company comply with certain guidelines promulgated by Google. Google may generally unilaterally update its policies and guidelines without advance notice. These updates may be specific to the Services Agreement or could be more general and thereby impact the Company as well as other companies. These policy and guideline updates have in the past and could in the future require modifications to, or prohibit and/or render obsolete certain of our products, services and/or business practices, which have been and could be costly to address and have had or otherwise could have an adverse effect on our financial condition and results of operations. As described below, Google has made changes to the policies under the Services Agreement and has also made industry-wide changes that have negatively impacted the Desktop business and it may do so in the future. Certain industry-wide policy changes became effective on July 1, 2019 and August 27, 2020. These industry-wide changes, combined with other changes to policies under the Services Agreement during the second half of 2019, have had a negative impact on the historical and expected future results of operations of the Desktop business. In addition, at multiple times during the fourth quarter of 2020, Google suspended services with respect to some of IAC’s products and may do so in the future. The Desktop business elected to modify certain marketing strategies in early January 2021. This is expected to further reduce the revenue and profitability of the Desktop business in 2021. The reduction in revenue and profitability was the primary factor in the goodwill and indefinite-lived intangible asset impairments related to the Desktop business recorded in the year ended December 31, 2020 of $265.1 million and $32.2 million respectively. The impact of COVD-19 was an additional factor. Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents. Cash and cash equivalents are maintained with financial institutions and are in excess of Federal Deposit Insurance Corporation insurance limits. Other Risks The Company is subject to certain risks and concentrations including dependence on third-party technology providers, exposure to risks associated with online commerce security and credit card fraud.
Building, Capitalized Software, Leasehold Improvements and Equipment	Building, Capitalized Software, Leasehold Improvements and Equipment Building, capitalized software, leasehold improvements and equipment are recorded at cost. Repairs and maintenance costs are expensed as incurred. Amortization of leasehold improvements, which is included within depreciation within the statement of operations, and depreciation is computed using the straight-line method over the estimated useful lives of the assets, or, in the case of leasehold improvements, the lease term, if shorter. ​ ​ ​ ​ ​ Estimated Asset Category ​ Useful Lives Buildings and leasehold improvements 3 Capitalized software and computer equipment 2 Furniture and other equipment 3 ​ The Company capitalizes certain internal use software costs including external direct costs utilized in developing or obtaining the software and compensation for personnel directly associated with the development of the software. Capitalization of such costs begins when the preliminary project stage is complete and ceases when the project is substantially complete and ready for its intended purpose. The net book value of capitalized internal use software is $68.0 million and $56.3 million at December 31, 2020 and 2019, respectively.
Business Combinations and Contingent Consideration Arrangements	Business Combinations and Contingent Consideration Arrangements The purchase price of each acquisition is attributed to the assets acquired and liabilities assumed based on their fair values at the date of acquisition, including identifiable intangible assets that either arise from a contractual or legal right or are separable from goodwill. The Company usually obtains the assistance of outside valuation experts to assist in the allocation of purchase price to the identifiable intangible assets acquired. While outside valuation experts may be used, management has ultimate responsibility for the valuation methods, models and inputs used and the resulting purchase price allocation. The excess purchase price over the value of net tangible and identifiable intangible assets acquired is recorded as goodwill and is assigned to the reporting unit(s) that is expected to benefit from the business combination as of the acquisition date. In connection with certain business combinations, the Company has entered into contingent consideration arrangements that are determined to be part of the purchase price. Each of these arrangements is initially recorded at its fair value at the time of the acquisition and reflected at current fair value for each subsequent reporting period thereafter until settled. Generally, our contingent consideration arrangements are based upon financial performance and/or operating metric targets. The Company generally determines the fair value of the contingent consideration arrangements by using probability-weighted analyses to determine the amounts of the gross liability, and, if the arrangement is long-term in nature, applying a discount rate that appropriately captures the risk associated with the obligation to determine the net amount reflected in the financial statements. Significant changes in forecasted earnings or operating metrics would result in a significantly higher or lower fair value measurement. The changes in the remeasured fair value of the contingent consideration arrangements during each reporting period, including the accretion of the discount, if applicable, are recognized in “General and administrative expense” in the accompanying statement of operations. See “Note 6—Financial Instruments and Fair Value Measurements” for a discussion of contingent consideration arrangements.
Goodwill and Indefinite-Lived Intangible Assets	Goodwill and Indefinite-Lived Intangible Assets The Company assesses goodwill and indefinite-lived intangible assets for impairment annually at October 1 or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit or the fair value of an indefinite-lived intangible asset below its carrying value. When the Company elects to perform a qualitative assessment and concludes it is not more likely than not that the fair value of the reporting unit is less than its carrying value, no further assessment of that reporting unit’s goodwill is necessary; otherwise, a quantitative assessment is performed and the fair value of the reporting unit is determined. If the carrying value of the reporting unit exceeds its estimated fair value, a goodwill impairment equal to the excess is recorded. For the Company’s annual goodwill test at October 1, 2020, a qualitative assessment of the ANGI, Vimeo, Care.com, Bluecrew and Nursefly reporting units’ goodwill was performed because the Company concluded it was more likely than not that the fair value of these reporting units was in excess of their respective carrying values. The primary factors that the Company considered in its qualitative assessment for each of these reporting units are described below: ● ANGI’s October 1, 2020 market capitalization of $5.5 billion exceeded its carrying value by approximately $4.3 billion. ● The Company prepared valuations of the Vimeo, Bluecrew and Nursefly reporting units primarily in connection with the issuance and/or settlement of equity awards that are denominated in the equity of these businesses during the year ended December 31, 2020. The valuations were prepared time proximate to, however, not as of, October 1, 2020. The fair value of each of these businesses was in excess of its October 1, 2020 carrying value. ● The primary factors the Company considered in its qualitative assessment of the Care.com reporting unit were the strong forecasted operating performance of the Care.com reporting unit and the excess of estimated fair value based upon the purchase price at acquisition over the carrying value at October 1, 2020. For the Company’s annual goodwill test at October 1, 2020, the Company quantitatively tested the Mosaic Group reporting unit. The Company’s quantitative test indicated that there was no impairment. The Company’s Dotdash, Ask Media Group, Desktop, The Daily Beast and IAC Films reporting units have no goodwill as of October 1, 2020. The aggregate carrying value of goodwill for which the most recent estimate of the excess of fair value over carrying value is less than 20% is approximately $759.5 million. The fair value of the Company’s reporting units (except for ANGI described above) is determined using both an income approach based on discounted cash flows (“DCF”) and a market approach when it tests goodwill for impairment, either on an interim basis or annual basis as of October 1 each year. The Company uses the same approach in determining the fair value of its businesses in connection with its non-public subsidiary denominated stock-based compensation plans, which can be a significant factor in the decision to apply the qualitative assessment rather than a quantitative test. Determining fair value using a DCF analysis requires the exercise of significant judgment with respect to several items, including the amount and timing of expected future cash flows and appropriate discount rates. The expected cash flows used in the DCF analyses are based on the Company’s most recent forecast and budget and, for years beyond the budget, the Company’s estimates, which are based, in part, on forecasted growth rates. The discount rates used in the DCF analyses are intended to reflect the risks inherent in the expected future cash flows of the respective reporting units. Assumptions used in the DCF analyses, including the discount rate, are assessed based on each reporting unit’s current results and forecasted future performance, as well as macroeconomic and industry specific factors. The discount rates used in the quantitative test for determining the fair value of the Company’s reporting units was 15.0% in 2020 (for the Mosaic reporting unit) and 12.5% in 2019 (for the Desktop reporting unit). Determining fair value using a market approach considers multiples of financial metrics based on both acquisitions and trading multiples of a selected peer group of companies. From the comparable companies, a representative market multiple is determined which is applied to financial metrics to estimate the fair value of a reporting unit. To determine a peer group of companies for our respective reporting units, we considered companies relevant in terms of consumer use, monetization model, margin and growth characteristics, and brand strength operating in their respective sectors. While the Company has the option to qualitatively assess whether it is more likely than not that the fair values of its indefinite-lived intangible assets are less than their carrying values, the Company’s policy is to determine the fair value of each of its indefinite-lived intangible assets annually as of October 1, in part, because the level of effort required to perform the quantitative and qualitative assessments is essentially equivalent. The Company determines the fair value of indefinite-lived intangible assets using an avoided royalty DCF valuation analysis. Significant judgments inherent in this analysis include the selection of appropriate royalty and discount rates and estimating the amount and timing of expected future cash flows. The discount rates used in the DCF analyses are intended to reflect the risks inherent in the expected future cash flows generated by the respective intangible assets. The royalty rates used in the DCF analyses are based upon an estimate of the royalty rates that a market participant would pay to license the Company’s trade names and trademarks. The future cash flows are based on the Company’s most recent forecast and budget and, for years beyond the budget, the Company’s estimates, which are based, in part, on forecasted growth rates. Assumptions used in the avoided royalty DCF analyses, including the discount rate and royalty rate, are assessed annually based on the actual and projected cash flows related to the asset, as well as macroeconomic and industry specific factors. The discount rates used in the Company’s annual indefinite-lived impairment assessment ranged from 11.5% to 25.0% in 2020 and 11.5% to 27.5% in 2019, and the royalty rates used in both 2020 and 2019 ranged from 1.0% to 5.5% . If the carrying value of an indefinite-lived intangible asset exceeds its estimated fair value, an impairment equal to the excess is recorded. There are no indefinite-lived intangible assets for which the most recent estimate of the excess fair value over carrying value is less than 20%. I n the quarter ended March 31, 2020, the Company determined that the effects of COVID-19 were an indicator of possible impairment for certain of its reporting units and indefinite-lived intangible assets and identified impairments of $212.0 million and $21.4 million related to the goodwill and certain indefinite-lived intangible assets, respectively, of the Desktop reporting unit. In the quarter ended September 30, 2020, the Company reassessed the fair values of the Desktop reporting unit and the related indefinite-lived intangible assets and recorded impairments equal to the remaining carrying value of the goodwill of $53.2 million and $10.8 million related to the intangible assets. The reduction in the Company’s fair value estimates of the Desktop business in the first and third quarters of 2020 was primarily due to lower consumer queries, increasing challenges in monetization and the reduced ability to market profitably due to policy changes implemented by Google and other browsers. The effects of COVID-19 on monetization were an additional factor. The October 1, 2020 annual assessment of goodwill and indefinite-lived intangible assets did not identify any additional impairments. The October 1, 2019 annual assessment of goodwill and indefinite-lived intangible assets identified a $3.3 million goodwill impairment charge and $0.7 million trade name impairment both related to the College Humor Media business. The October 1, 2018 annual assessment of goodwill did not identify any impairments. The 2018 annual assessment of indefinite-lived intangible assets identified impairment charges of $27.7 million and $1.1 million related to certain Desktop and College Humor Media indefinite-lived trade names, respectively. The indefinite-lived intangible asset impairment charge at Desktop was due to Google’s policy changes related to its Chrome browser which became effective on September 12, 2018 and have negatively impacted the distribution of the Company’s B2C downloadable desktop products. The impairment charge related to the B2C trade name was identified in the Company’s IAC’s annual impairment assessment as of October 1, 2018 and reflects the projected reduction in profits and revenues and the resultant reduction in the assumed royalty rate from these policy changes. The impairment charges are included in “Amortization of intangibles” in the accompanying statement of operations. The Company’s operating segments are ANGI, Vimeo, Dotdash and Search, which are also reportable segments, and within its Emerging & Other reportable segment, Mosaic Group, Care.com, Bluecrew, Nursefly, The Daily Beast and IAC Films. The Company’s reporting units are consistent with its operating segments, with the exception of Desktop and Ask Media Group, which are separate reporting units within the Search operating segment. Goodwill is tested for impairment at the reporting unit level. See “Note 12—Segment Information” for additional information regarding the Company’s method of determining operating and reportable segments.
Long-Lived Assets and Intangible Assets with Definite Lives	Long-Lived Assets and Intangible Assets with Definite Lives Long-lived assets, which consist of ROU assets, building, capitalized software, leasehold improvements and equipment, and intangible assets with definite lives, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. The carrying value of a long-lived asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. If the carrying value is deemed not to be recoverable, an impairment loss is recorded equal to the amount by which the carrying value of the long-lived asset exceeds its fair value. Amortization of definite-lived intangible assets is computed either on a straight-line basis or based on the pattern in which the economic benefits of the asset are expected to be realized.
Fair Value Measurements	Fair Value Measurements The Company categorizes its financial instruments measured at fair value into a fair value hierarchy that prioritizes the inputs used in pricing the asset or liability. The three levels of the fair value hierarchy are: ● Level 1: Observable inputs obtained from independent sources, such as quoted market prices for identical assets and liabilities in active markets. ● Level 2: Other inputs, which are observable directly or indirectly, such as quoted market prices for similar assets or liabilities in active markets, quoted market prices for identical or similar assets or liabilities in markets that are not active and inputs that are derived principally from or corroborated by observable market data. The fair values of the Company’s Level 2 financial assets are primarily obtained from observable market prices for identical underlying securities that may not be actively traded. Certain of these securities may have different market prices from multiple market data sources, in which case an average market price is used. ● Level 3: Unobservable inputs for which there is little or no market data and require the Company to develop its own assumptions, based on the best information available in the circumstances, about the assumptions market participants would use in pricing the assets or liabilities. See “Note 6—Financial Instruments and Fair Value Measurements” for a discussion of fair value measurements made using Level 3 inputs. The Company’s non-financial assets, such as goodwill, intangible assets, ROU assets and property and equipment are adjusted to fair value only when an impairment is recognized. The Company’s financial assets, comprising equity securities without readily determinable fair values, are adjusted to fair value when observable price changes are identified or an impairment is recognized. Such fair value measurements are based predominantly on Level 3 inputs.
Advertising Costs	Advertising Costs Advertising costs are expensed in the period incurred (when the advertisement first runs for production costs that are initially capitalized) and represent online marketing, including fees paid to search engines, social media sites and third parties that distribute our B2C downloadable applications, offline marketing, which is primarily television advertising, and partner-related payments to those who direct traffic to the brands within our ANGI segment. Advertising expense is $862.2 million, $855.2 million and $798.1 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company capitalizes and amortizes the costs associated with certain distribution arrangements that require us to pay a fee per access point delivered. These access points are generally in the form of downloadable applications associated with our direct-to consumer operations. These fees are amortized over the estimated useful lives of the access points to the extent the Company can reasonably estimate a probable future economic benefit and the period over which such benefit will be realized (generally 18 months ). Otherwise, the fees are charged to expense as incurred.
Legal Costs	Legal Costs Legal costs are expensed as incurred.
Income Taxes	Income Taxes The Company was included within Old IAC’s tax group for purposes of federal and consolidated state income tax return filings through June 30, 2020, the date of the MTCH Separation. For periods prior thereto, the income tax benefit and/or provision was computed for the Company on an as if standalone, separate return basis and payments to and refunds from Old IAC for the Company’s share of Old IAC’s consolidated federal and state tax return liabilities/receivables calculated on this basis have been reflected within cash flows from operating activities in the accompanying statement of cash flows. The Company accounts for income taxes under the liability method, and deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying values of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. A valuation allowance is provided if it is determined that it is more likely than not that the deferred tax asset will not be realized. The Company records interest, net of any applicable related income tax benefit, on potential income tax contingencies as a component of income tax expense. The Company evaluates and accounts for uncertain tax positions using a two-step approach. Recognition (step one) occurs when the Company concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustainable upon examination. Measurement (step two) determines the amount of benefit that is greater than 50% likely to be realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. De-recognition of a tax position that was previously recognized would occur when the Company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained.
Earnings Per Share	Earnings Per Share Basic earnings per share is computed by dividing net earnings attributable to IAC shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per share reflects the potential dilution that could occur if stock options and other commitments to issue common stock were exercised or equity awards vested resulting in the issuance of common stock that could share in the earnings of the Company. For periods prior to the MTCH Separation, the Company calculated basic and diluted earnings per share using the shares issued on June 30, 2020, the date of the MTCH Separation. See “Note 10—Earnings Per Share” for additional information on dilutive securities.
Foreign Currency Translation and Transaction Gains and Losses	Foreign Currency Translation and Transaction Gains and Losses The financial position and operating results of foreign entities whose primary economic environment is based on their local currency are consolidated using the local currency as the functional currency. These local currency assets and liabilities are translated at the rates of exchange as of the balance sheet date, and local currency revenue and expenses of these operations are translated at average rates of exchange during the period. Translation gains and losses are included in accumulated other comprehensive income as a component of shareholders’ and parent’s equity. Transaction gains and losses resulting from assets and liabilities denominated in a currency other than the functional currency are included in the statement of operations as a component of other (expense) income, net. See “Note 17—Financial Statement Details” for additional information regarding foreign currency exchange gains and losses. Translation gains and losses relating to foreign entities that are liquidated or substantially liquidated are reclassified out of accumulated other comprehensive income (loss) into earnings. During the years ended December 31, 2020 and 2018, a gain of $0.1 million and a loss of $0.1 million, respectively, were reclassified into earning, and were included in “Other (expense) income, net” in the accompanying statement of operations. There were no such gains or losses for the year ended December 31, 2019.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation is measured at the grant date based on the fair value of the award and is generally expensed over the requisite service period. See “Note 11—Stock-based Compensation” for a discussion of the Company’s stock-based compensation plans.
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests Noncontrolling interests in the subsidiaries of the Company are ordinarily reported on the balance sheet within shareholders’ equity, separately from the Company’s equity. However, securities that are redeemable at the option of the holder and not solely within the control of the issuer must be classified outside of shareholders’ equity. Accordingly, all noncontrolling interests that are redeemable at the option of the holder are presented outside of shareholders’ and parents’ equity in the accompanying balance sheet. In connection with the acquisition of certain subsidiaries, management of these businesses has retained an ownership interest. The Company is party to fair value put and call arrangements with respect to these interests. These put and call arrangements allow management of these businesses to require the Company to purchase their interests or allow the Company to acquire such interests at fair value, respectively. The put arrangements do not meet the definition of a derivative instrument as the put agreements do not provide for net settlement. These put and call arrangements become exercisable by the Company and the counter-party at various dates in the future. One of these arrangements was exercised during both of the years ended December 31, 2020 and 2019 and two of these arrangements were exercised during the year ended December 31, 2018. These put arrangements are exercisable by the counter-party outside the control of the Company. Accordingly, to the extent that the fair value of these interests exceeds the value determined by normal noncontrolling interest accounting, the value of such interests is adjusted to fair value with a corresponding adjustment to additional paid-in capital or invested capital. During the years ended December 31, 2020, 2019 and 2018, the Company recorded adjustments of $183.3 million, $11.6 million and $6.6 million, respectively, to increase these interests to fair value. Fair value determinations require high levels of judgment and are based on various valuation techniques, including market comparables and discounted cash flow projections.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Pronouncements Adopted by IAC ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The Company adopted ASU No. 2016-13 effective January 1, 2020. ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes The Company adopted ASU No. 2019-12 effective January 1, 2020, which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes Accounting Pronouncements Not Yet Adopted by IAC There are no recently issued accounting pronouncements that have not yet been adopted that are expected to have a material effect on the results of operations, financial condition or cash flows of the Company.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified to conform to the current year presentation.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of Changes in the Allowance for Credit Losses	The following table presents the changes in the allowance for credit losses for the year ended December 31, 2020: ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ (In thousands) Balance at January 1 ​ $ 20,257 Current period provision for credit losses ​ 80,765 Write-offs charged against the allowance ​ (75,815) Recoveries collected ​ 2,447 Balance at December 31 ​ $ 27,654
Schedule of Estimated Useful Lives of Property and Equipment	​ ​ ​ ​ ​ Estimated Asset Category ​ Useful Lives Buildings and leasehold improvements 3 Capitalized software and computer equipment 2 Furniture and other equipment 3 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Building, capitalized software, leasehold improvements and equipment ​ ​ Buildings and leasehold improvements ​ $ 198,778 ​ $ 242,882 Capitalized software and computer equipment ​ 149,789 ​ 124,523 Furniture and other equipment ​ 84,161 ​ 84,640 Land ​ — ​ 11,591 Projects in progress ​ 53,635 ​ 43,576 Building, capitalized software, leasehold improvements and equipment ​ 486,363 ​ 507,212 Accumulated depreciation and amortization ​ (208,112) ​ (201,798) Building, capitalized software, leasehold improvements and equipment, net ​ $ 278,251 ​ $ 305,414

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income before Income Taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) U.S. ​ $ 197,545 ​ $ (74,360) ​ $ 269,267 Foreign ​ 12,022 ​ 46,054 ​ 36,304 Total ​ $ 209,567 ​ $ (28,306) ​ $ 305,571
Schedule of Components of Income Tax Expense (Benefit)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Current income tax (benefit) provision: ​ ​ ​ ​ ​ ​ Federal ​ $ (29,176) ​ $ (1,117) ​ $ (1,187) State ​ 2,253 ​ 197 ​ 1,514 Foreign ​ (176) ​ 3,201 ​ 4,108 Current income tax (benefit) provision ​ (27,099) ​ 2,281 ​ 4,435 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred income tax (benefit) provision: ​ ​ ​ Federal ​ (20,054) ​ (51,952) ​ 20,156 State ​ (7,726) ​ (10,645) ​ (7,272) Foreign ​ (4,140) ​ (173) ​ (4,119) Deferred income tax (benefit) provision ​ (31,920) ​ (62,770) ​ 8,765 Income tax (benefit) provision ​ $ (59,019) ​ $ (60,489) ​ $ 13,200
Schedule of Deferred Tax Assets and Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Deferred tax assets: ​ ​ ​ Net operating loss carryforwards ​ $ 404,807 ​ $ 201,766 Stock-based compensation ​ 44,926 ​ 62,566 Long-term lease liabilities ​ 58,800 ​ 42,486 Tax credit carryforwards ​ 48,936 ​ 38,066 Accrued expenses ​ 20,490 ​ 12,911 Other ​ 34,024 ​ 21,039 Total deferred tax assets ​ 611,983 ​ 378,834 Less: valuation allowance ​ (113,684) ​ (92,990) Net deferred tax assets ​ 498,299 ​ 285,844 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ Investment in subsidiaries ​ (242,537) ​ (240,420) Investment in MGM Resorts International ​ (197,998) ​ — Right-of-use assets ​ (43,418) ​ (29,654) Intangible assets ​ (30,094) ​ (28,488) Other ​ (34,639) ​ (31,534) Total deferred tax liabilities ​ (548,686) ​ (330,096) Net deferred tax liabilities ​ $ (50,387) ​ $ (44,252)
Schedule of Effective Income Tax Rate Reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Income tax provision (benefit) at the federal statutory rate of 21% ​ $ 44,009 ​ $ (5,944) ​ $ 64,170 State income taxes, net of effect of federal tax benefit ​ 15,936 ​ (277) ​ 5,188 Stock-based compensation ​ (167,998) ​ (56,871) ​ (39,326) Non-deductible goodwill impairment ​ 53,012 ​ — ​ — Non-deductible executive compensation ​ 14,219 ​ 7,409 ​ 2,983 Change in valuation allowance on capital losses ​ 11,385 ​ (5,815) ​ (1,280) Research credit ​ (7,407) ​ (5,105) ​ (3,167) Amortizable tax basis related to intercompany transaction ​ (7,044) ​ — ​ — Non-deductible expenses ​ 6,556 ​ 5,460 ​ 1,727 Change in judgement on beginning of the year valuation allowance ​ (3,544) ​ — ​ — Net adjustment related to the reconciliation of income tax provision accruals to tax returns ​ (2,591) ​ 138 ​ 42 Deferred tax adjustment for enacted changes in tax laws and rates ​ (14,579) ​ (687) ​ (13,646) Other, net ​ (973) ​ 1,203 ​ (3,491) Income tax (benefit) provision ​ $ (59,019) ​ $ (60,489) ​ $ 13,200
Schedule of Income Tax Contingencies	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Balance at January 1 ​ $ 18,060 ​ $ 15,451 ​ $ 14,528 Additions based on tax positions related to the current year ​ 3,977 ​ 2,781 ​ 1,455 Settlements ​ (4,309) ​ — ​ — Additions for tax positions of prior years ​ 2,781 ​ 238 ​ 235 Expiration of applicable statutes of limitations ​ ​ (351) ​ ​ (410) ​ ​ (767) Balance at December 31 ​ $ 20,158 ​ $ 18,060 ​ $ 15,451

BUSINESS COMBINATION (Tables)

BUSINESS COMBINATION (Tables)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Schedule of Preliminary Estimated Fair Value of Assets Acquired and Liabilities Assumed	​ ​ ​ ​ ​ ​ Care.com ​ ​ (In thousands) Cash and cash equivalents ​ $ 57,702 Short-term investments ​ 20,000 Accounts receivable ​ 20,213 Other current assets ​ 7,479 Property and equipment ​ 2,894 Goodwill ​ 404,313 Intangible assets ​ 116,800 Deferred income taxes ​ 32,112 Other non-current assets ​ 30,444 Total assets ​ 691,957 Deferred revenue ​ (13,422) Other current liabilities ​ (39,698) Deferred income taxes ​ (25,824) Other non-current liabilities ​ (26,039) Net assets acquired ​ $ 586,974
Schedule of Preliminary Estimated Fair Value of Intangible Assets Acquired	​ ​ ​ ​ ​ ​ ​ ​ ​ Care.com ​ ​ ​ Useful Life ​ ​ (In thousands) ​ (Years) Indefinite-lived trade name and trademarks ​ $ 59,300 Indefinite Developed technology ​ 21,200 2 Customer relationships ​ 35,500 2 - 5 Provider relationships ​ 800 4 Total identifiable intangible assets acquired ​ $ 116,800 ​
Schedule of Pro Forma Financial Information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 ​ ​ (In thousands, except per share data) Revenue ​ $ 3,090,779 ​ $ 2,904,243 Net earnings (loss) attributable to IAC shareholders ​ $ 296,933 ​ $ (16,926) Basic earnings (loss) per share attributable to IAC shareholders ​ $ 3.48 ​ $ (0.20) Diluted earnings (loss) per share attributable to IAC shareholders ​ $ 3.26 ​ $ (0.20)

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets, Net	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Goodwill ​ $ 1,879,438 ​ $ 1,616,867 Intangible assets with indefinite lives ​ 246,913 ​ 225,296 Intangible assets with definite lives, net of accumulated amortization ​ 158,927 ​ 124,854 Total goodwill and intangible assets, net ​ $ 2,285,278 ​ $ 1,967,017
Schedule of Goodwill by Reporting Unit	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Balance at ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ December 31, ​ 2019 Additions (Deductions) Impairment Translation 2020 ​ ​ (In thousands) ANGI Homeservices ​ $ 884,296 ​ $ 2,665 ​ $ — ​ $ — ​ $ 5,172 ​ $ 892,133 Vimeo ​ 219,374 ​ — ​ (38) ​ — ​ — ​ 219,336 Search ​ 265,146 ​ — ​ — ​ (265,146) ​ — ​ — Emerging & Other ​ 248,051 ​ 519,405 ​ — ​ — ​ 513 ​ 767,969 Total ​ $ 1,616,867 ​ $ 522,070 ​ $ (38) ​ $ (265,146) ​ $ 5,685 ​ $ 1,879,438 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Balance at ​ ​ December 31, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ December 31, ​ 2018 Additions (Deductions) Impairment Translation 2019 ​ ​ (In thousands) ANGI Homeservices ​ $ 895,071 ​ $ 18,326 ​ $ (29,293) ​ $ — ​ $ 192 ​ $ 884,296 Vimeo ​ 77,152 ​ 142,222 ​ — ​ — ​ — ​ 219,374 Search ​ 265,146 ​ — ​ — ​ — ​ — ​ 265,146 Emerging & Other ​ 246,748 ​ 4,765 ​ — ​ (3,318) ​ (144) ​ 248,051 Total ​ $ 1,484,117 ​ $ 165,313 ​ $ (29,293) ​ $ (3,318) ​ $ 48 ​ $ 1,616,867
Schedule of Intangible Assets with Definite Lives	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ Gross ​ ​ ​ ​ ​ ​ ​ Average ​ ​ Carrying ​ Accumulated ​ ​ ​ ​ Useful Life ​ Amount Amortization Net (Years) ​ ​ (In thousands) ​ ​ Technology ​ $ 167,997 ​ $ (102,355) ​ $ 65,642 4.1 Service professional relationships ​ 97,960 ​ (97,312) ​ 648 3.0 Customer lists and user base ​ 91,887 ​ (33,864) ​ 58,023 4.0 Trade names ​ 53,383 ​ (19,227) ​ 34,156 6.6 Memberships ​ 15,900 ​ (15,900) ​ — 3.0 Other ​ 10,439 ​ (9,981) ​ 458 3.4 Total ​ $ 437,566 ​ $ (278,639) ​ $ 158,927 4.1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ Gross ​ ​ ​ ​ ​ ​ ​ Average ​ ​ Carrying ​ Accumulated ​ ​ ​ ​ Useful Life ​ Amount Amortization Net (Years) ​ ​ (In thousands) ​ ​ Technology ​ $ 143,255 ​ $ (73,483) ​ $ 69,772 4.5 Service professional relationships ​ 99,651 ​ (76,445) ​ 23,206 2.9 Customer lists and user base ​ 44,286 ​ (24,226) ​ 20,060 3.3 Trade names ​ 12,777 ​ (8,082) ​ 4,695 3.5 Memberships ​ 15,900 ​ (11,940) ​ 3,960 3.0 Other ​ 10,439 ​ (7,278) ​ 3,161 3.4 Total ​ $ 326,308 ​ $ (201,454) ​ $ 124,854 3.7
Schedule of Expected Amortization of Intangible Assets	​ ​ ​ ​ ​ Years Ending December 31, (In thousands) 2021 ​ $ 62,600 2022 ​ 37,982 2023 ​ 23,209 2024 ​ 11,292 2025 ​ 9,040 Thereafter ​ 14,804 Total ​ $ 158,927

FINANCIAL INSTRUMENTS AND FAI_2

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Current Available-for-sale Marketable Securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ ​ Cost Gains Losses Fair Value ​ ​ (In thousands) Treasury discount notes ​ $ 224,976 ​ $ 3 ​ $ — ​ $ 224,979 Total available-for-sale marketable debt securities ​ $ 224,976 ​ $ 3 ​ $ — ​ $ 224,979
Schedule of Long-term Investments	Investment in MGM Resorts International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Investment in MGM Resorts International (“MGM”) ​ $ 1,860,158 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Equity securities without readily determinable fair values ​ $ 296,491 ​ $ 347,975 Equity method investment ​ 1,152 ​ — Total long-term investments ​ $ 297,643 ​ $ 347,975
Schedule of Realized and Unrealized Gains (Losses) on Investments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 ​ ​ (In thousands) Upward adjustments (gross unrealized gains) ​ $ — ​ $ 19,698 Downward adjustments including impairments (gross unrealized losses) ​ (51,484) ​ (1,193) Total ​ $ (51,484) ​ $ 18,505 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Realized gains, net, for equity securities sold ​ $ 2,161 ​ $ 22,880 ​ $ 27,366 Unrealized gains, net, on equity securities held ​ 797,565 ​ 18,505 ​ 126,063 Total gains recognized, net ​ $ 799,726 ​ $ 41,385 ​ $ 153,429
Schedule of Financial Instruments Measured at Fair Value on Recurring Basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Quoted Market ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Prices in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ Total ​ ​ Identical Assets ​ Inputs ​ Inputs ​ Fair Value ​ (Level 1) (Level 2) (Level 3) Measurements ​ ​ (In thousands) Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 1,874,091 ​ $ — ​ $ — ​ $ 1,874,091 Treasury discount notes ​ — ​ 1,224,966 ​ — ​ 1,224,966 Time deposits ​ — ​ 3,265 ​ — ​ 3,265 Marketable debt securities: ​ ​ ​ ​ Treasury discount notes ​ — ​ 224,979 ​ — ​ 224,979 Investment in MGM Resorts International ​ 1,860,158 ​ — ​ — ​ 1,860,158 Other non-current assets: ​ ​ ​ ​ Warrant ​ — ​ — ​ 5,276 ​ 5,276 Total ​ $ 3,734,249 ​ $ 1,453,210 ​ $ 5,276 ​ $ 5,192,735 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Contingent consideration arrangement ​ $ — ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Quoted Market ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Prices in Active ​ Other ​ Significant ​ ​ ​ ​ ​ Markets for ​ Observable ​ Unobservable ​ Total ​ ​ Identical Assets ​ Inputs ​ Inputs ​ Fair Value ​ (Level 1) (Level 2) (Level 3) Measurements ​ ​ (In thousands) Assets: ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ Money market funds ​ $ 699,589 ​ $ — ​ $ — ​ $ 699,589 Time deposits ​ — ​ 23,075 ​ — ​ 23,075 Other non-current assets: ​ ​ ​ ​ Warrant ​ — ​ — ​ 8,495 ​ 8,495 Total ​ $ 699,589 ​ $ 23,075 ​ $ 8,495 ​ $ 731,159 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Contingent consideration arrangement ​ $ — ​ $ — ​ $ (6,918) ​ $ (6,918)
Schedule of Unobservable Inputs in Fair Value Measurement	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2020 ​ 2019 ​ ​ ​ ​ ​ Contingent ​ ​ ​ ​ Contingent ​ ​ ​ ​ ​ Consideration ​ ​ ​ ​ Consideration ​ Warrant Arrangements Warrant Arrangement ​ ​ (In thousands) Balance at January 1 ​ $ 8,495 ​ $ (6,918) ​ $ — ​ $ (26,657) Fair value at date of acquisition ​ — ​ (1,000) ​ 17,618 ​ — Total net (losses) gains: ​ ​ ​ ​ Included in earnings: ​ ​ ​ ​ Fair value adjustments ​ (3,219) ​ 6,918 ​ (9,123) ​ 19,739 Settlements ​ — ​ 1,000 ​ — ​ — Balance at December 31 ​ $ 5,276 ​ $ — ​ $ 8,495 ​ $ (6,918)
Schedule of Carrying Value and the Fair Value of Financial Instruments Measured at Fair Value Only for Disclosure Purposes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ ​ Carrying ​ Fair ​ Carrying ​ Fair ​ Value Value Value Value ​ ​ (In thousands) Notes receivable—related party, current ​ $ — ​ $ — ​ $ 55,251 ​ $ 55,251 Current portion of long-term debt ​ $ — ​ $ — ​ $ (13,750) ​ $ (13,681) Long-term debt, net (a) ​ $ (712,277) ​ $ (725,700) ​ $ (231,946) ​ $ (232,581)

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) 3.875% ANGI Group Senior Notes due August 15, 2028 (“ANGI Group Senior Notes”); interest payable each February 15 and August 15, commencing February 15, 2021 ​ $ 500,000 ​ $ — ANGI Group Term Loan due November 5, 2023 (“ANGI Group Term Loan”) ​ 220,000 ​ 247,500 Total long-term debt ​ 720,000 ​ 247,500 Less: current portion of ANGI Group Term Loan ​ — ​ 13,750 Less: unamortized debt issuance costs ​ 7,723 ​ 1,804 Total long-term debt, net ​ $ 712,277 ​ $ 231,946
Schedule of Debt Instrument Redemption	​ ​ ​ ​ ​ Year Percentage 2023 101.938 % 2024 100.969 % 2025 and thereafter 100.000 %
Schedule of Aggregate Contractual Maturities of Long-term Debt	​ ​ ​ ​ ​ Years Ending December 31, (In thousands) 2022 ​ $ 27,500 2023 ​ 192,500 2028 ​ 500,000 Total ​ 720,000 Less: unamortized debt issuance costs ​ 7,723 Total long-term debt, net ​ $ 712,277

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ ​ ​ Unrealized Gains ​ ​ ​ ​ ​ Foreign ​ On Available- ​ Accumulated ​ ​ Currency ​ For-Sale ​ Other ​ ​ Translation ​ Marketable Debt ​ Comprehensive ​ Adjustment Securities (Loss) Income ​ ​ (In thousands) Balance at January 1 ​ $ (12,226) ​ $ — ​ $ (12,226) Other comprehensive income before reclassifications ​ 6,236 ​ 2 ​ 6,238 Amounts reclassified to earnings ​ (144) ​ — ​ (144) Net current period other comprehensive income ​ 6,092 ​ 2 ​ 6,094 Accumulated other comprehensive income allocated to noncontrolling interests during the period ​ (38) ​ — ​ (38) Balance at December 31 ​ $ (6,172) ​ $ 2 ​ $ (6,170) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ ​ ​ Unrealized Gains ​ ​ ​ ​ ​ Foreign ​ On Available- ​ Accumulated ​ ​ Currency ​ For-Sale ​ Other ​ ​ Translation ​ Marketable Debt ​ Comprehensive ​ Adjustment Securities (Loss) Income ​ ​ (In thousands) Balance at January 1 ​ $ (12,543) ​ $ 2 ​ $ (12,541) Other comprehensive income (loss) ​ 337 ​ (2) ​ 335 Net current period other comprehensive income (loss) ​ 337 ​ (2) ​ 335 Accumulated other comprehensive income allocated to noncontrolling interests during the period ​ (20) ​ — ​ (20) Balance at December 31 ​ $ (12,226) ​ $ — ​ $ (12,226) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2018 ​ ​ ​ ​ ​ Unrealized Gains ​ ​ ​ ​ ​ Foreign ​ On Available- ​ Accumulated ​ ​ Currency ​ For-Sale ​ Other ​ ​ Translation ​ Marketable Debt ​ Comprehensive ​ Adjustment Securities Loss ​ ​ (In thousands) Balance at January 1 ​ $ (7,504) ​ $ — ​ $ (7,504) Other comprehensive (loss) income before reclassifications ​ (4,976) ​ 2 ​ (4,974) Amounts reclassified to earnings ​ (52) ​ — ​ (52) Net current period other comprehensive (loss) income ​ (5,028) ​ 2 ​ (5,026) Accumulated other comprehensive income allocated to noncontrolling interests during the period ​ (11) ​ — ​ (11) Balance at December 31 ​ $ (12,543) ​ $ 2 ​ $ (12,541)

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Earnings per Share	The following table sets forth the computation of basic and diluted earnings per share attributable to IAC shareholders: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 ​ Basic Diluted Basic Diluted Basic Diluted ​ ​ (In thousands, except per share data) Numerator: ​ ​ ​ ​ ​ ​ Net earnings ​ $ 268,586 ​ $ 268,586 ​ $ 32,183 ​ $ 32,183 ​ $ 292,371 ​ $ 292,371 Net loss (earnings) attributable to noncontrolling interests ​ 1,140 ​ 1,140 ​ (9,288) ​ (9,288) ​ (45,599) ​ (45,599) Impact from public subsidiaries’ dilutive securities (a) ​ — ​ 71 ​ — ​ — ​ — ​ — Net earnings attributable to IAC shareholders ​ $ 269,726 ​ $ 269,797 ​ $ 22,895 ​ $ 22,895 ​ $ 246,772 ​ $ 246,772 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: ​ ​ ​ ​ ​ ​ Weighted average basic shares outstanding (b) ​ 85,355 ​ 85,355 ​ 85,132 ​ 85,132 ​ 85,132 ​ 85,132 Dilutive securities (a) (c) (d) (e) ​ — ​ 5,593 ​ — ​ — ​ — ​ — Denominator for earnings per share—weighted average shares (a) (c) (d) (e) ​ 85,355 ​ 90,948 ​ 85,132 ​ 85,132 ​ 85,132 ​ 85,132 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share attributable to IAC shareholders: ​ ​ ​ ​ ​ ​ Earnings per share ​ $ 3.16 ​ $ 2.97 ​ $ 0.27 ​ $ 0.27 ​ $ 2.90 ​ $ 2.90 (a) IAC has the option to settle certain ANGI stock-based awards in its shares. For the year ended December 31, 2020, it is more dilutive for IAC to settle these ANGI equity awards. (b) On November 5, 2020, the Company granted 3,000,000 shares of IAC restricted common stock to its Chief Executive Officer (“CEO”), that cliff vest on the ten-year anniversary of the grant date based on satisfaction of IAC’s stock price targets and continued employment through the vesting date. These shares are included in common stock outstanding at December 31, 2020 on the balance sheet, however, are excluded from weighted average basic shares outstanding in the table above in calculating earnings per share for the year ended December 31, 2020. (c) If the effect is dilutive, weighted average common shares outstanding include the incremental shares that would be issued upon the assumed exercise of stock options and subsidiary denominated equity, vesting of restricted common stock, restricted stock units (“RSUs”) and market-based awards (“MSUs”). For the year ended December 31, 2020, 3.1 million potentially dilutive securities were excluded from the calculation of diluted earnings per share because their inclusion would have been anti-dilutive. (d) The Company computed basic and diluted earnings per share for periods prior to the MTCH Separation using the shares issued on June 30, 2020 in connection with the MTCH Separation. (e) See “Note 11—Stock-based Compensation” for additional information on the grant of IAC restricted common stock to its CEO and equity instruments denominated in the shares of certain subsidiaries .

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Outstanding Unvested RSUs and MSUs	Unvested RSUs and MSUs outstanding at December 31, 2020 and changes during the period ended December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ RSUs ​ MSUs ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ Average ​ ​ Number ​ Grant Date ​ Number ​ Grant Date ​ of Shares Fair Value of Shares Fair Value ​ ​ (Shares in thousands) Unvested on June 30, 2020, the date of the MTCH Separation 421 ​ $ 48.13 347 ​ $ 44.76 Granted 1,121 ​ 128.82 — ​ — Vested (26) ​ 64.52 (347) ​ 44.76 Forfeited (13) ​ 94.17 — ​ — Unvested at December 31, 2020 1,503 ​ $ 107.62 — ​ $ — ​
Schedule of Changes in Outstanding Stock Options	Stock options outstanding at December 31, 2020 and changes during the period ended December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ Shares Price Term in Years Value ​ ​ (Shares and intrinsic value in thousands) Old IAC options converted into IAC options on June 30, 2020, the date of the MTCH Separation 4,498 ​ $ 20.08 ​ Granted — ​ — ​ Exercised (587) ​ 13.46 ​ Forfeited — ​ — ​ Expired (2) ​ 14.05 ​ Options outstanding at December 31, 2020 3,909 ​ $ 21.08 4.9 ​ $ 657,704 Options exercisable 3,909 ​ $ 21.08 4.9 ​ $ 657,704 ​
Schedule of Information for Stock Options Outstanding and Exercisable	The following table summarizes the information about stock options outstanding and exercisable at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ Options Exercisable ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ Average ​ Weighted- ​ ​ ​ Average ​ Weighted- ​ ​ Outstanding at ​ Remaining ​ Average ​ Exercisable at ​ Remaining ​ Average ​ ​ December 31, ​ Contractual ​ Exercise ​ December 31, ​ Contractual ​ Exercise Range of Exercise Prices 2020 Life in Years Price 2020 Life in Years Price ​ ​ (Shares in thousands) Less than $20.00 1,060 4.7 ​ $ 14.21 1,060 4.7 ​ $ 14.21 $20.01 to $30.00 2,765 4.9 ​ 22.96 2,765 4.9 ​ 22.96 $30.01 to $40.00 4 6.6 ​ 31.82 4 6.6 ​ 31.82 $40.01 to $50.00 80 7.2 ​ 46.61 80 7.2 ​ 46.61 ​ 3,909 4.9 ​ $ 21.08 3,909 4.9 ​ $ 21.08

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of Segment Reporting Information	The following table presents revenue by reportable segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Revenue: ​ ​ ​ ANGI Homeservices ​ $ 1,467,925 ​ $ 1,326,205 ​ $ 1,132,241 Vimeo ​ 283,218 ​ 196,015 ​ 159,641 Dotdash ​ 213,753 ​ 167,594 ​ 130,991 Search ​ 613,274 ​ 742,184 ​ 823,950 Emerging & Other ​ 469,759 ​ 274,107 ​ 286,586 Inter-segment eliminations ​ (248) ​ (304) ​ (361) Total ​ $ 3,047,681 ​ $ 2,705,801 ​ $ 2,533,048
Schedule of Revenue by Geographic Areas	Revenue by geography is based on where the customer is located. Geographic information about revenue and long-lived assets is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Revenue: ​ ​ ​ United States ​ $ 2,449,257 ​ $ 2,097,743 ​ $ 1,951,957 All other countries ​ 598,424 ​ 608,058 ​ 581,091 Total ​ $ 3,047,681 ​ $ 2,705,801 ​ $ 2,533,048 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Long-lived assets (excluding goodwill, intangible assets and ROU assets): ​ ​ United States ​ $ 266,169 ​ $ 297,433 All other countries ​ 12,082 ​ 7,981 Total ​ $ 278,251 ​ $ 305,414 ​
Schedule of Long-lived Assets by Geographic Areas	The following table presents the revenue of the Company’s segments disaggregated by type of service: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) ANGI Homeservices ​ ​ ​ Marketplace: ​ ​ ​ Consumer connection revenue (a) ​ $ 1,054,660 ​ $ 913,533 ​ $ 704,341 Service professional membership subscription revenue ​ 50,975 ​ 63,872 ​ 66,214 Other revenue ​ 25,685 ​ 15,263 ​ 3,940 Total Marketplace revenue ​ 1,131,320 ​ 992,668 ​ 774,495 Advertising and other revenue (b) ​ 264,108 ​ 257,224 ​ 287,676 Total North America revenue ​ 1,395,428 ​ 1,249,892 ​ 1,062,171 Consumer connection revenue (c) ​ 57,692 ​ 59,611 ​ 50,913 Service professional membership subscription revenue ​ 13,091 ​ 14,231 ​ 17,362 Advertising and other revenue ​ 1,714 ​ 2,471 ​ 1,795 Total Europe revenue ​ 72,497 ​ 76,313 ​ 70,070 Total ANGI Homeservices revenue ​ $ 1,467,925 ​ $ 1,326,205 ​ $ 1,132,241 (a) Includes fees paid by service professionals for consumer matches and revenue from pre-priced jobs sourced through the HomeAdvisor and Handy platforms. (b) Includes Angie’s List revenue from service professionals under contract for advertising and Angie’s List membership subscription fees from consumers, as well as revenue from mHelpDesk, HomeStars, and Felix. Felix was sold on December 31, 2018 and its revenue for the year ended December 31, 2018 was $36.9 million. (c) Includes fees paid by service professionals for consumer matches. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 ​ (In thousands) Vimeo ​ ​ ​ ​ ​ ​ ​ ​ ​ Platform revenue ​ $ 283,218 $ 193,736 $ 146,665 Hardware revenue ​ — ​ 2,279 ​ 12,976 Total Vimeo revenue ​ $ 283,218 ​ $ 196,015 ​ $ 159,641 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Dotdash ​ ​ ​ Display advertising revenue ​ $ 137,455 ​ $ 126,350 ​ $ 103,704 Performance marketing revenue ​ 76,298 ​ 41,244 ​ 27,287 Total Dotdash revenue ​ $ 213,753 ​ $ 167,594 ​ $ 130,991 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Search ​ ​ ​ Advertising revenue: ​ ​ ​ Google advertising revenue ​ $ 506,077 ​ $ 678,438 ​ $ 770,494 Non-Google advertising revenue ​ 90,286 ​ 47,583 ​ 31,975 Total advertising revenue ​ 596,363 ​ 726,021 ​ 802,469 Other revenue ​ 16,911 ​ 16,163 ​ 21,481 Total Search revenue ​ $ 613,274 ​ $ 742,184 ​ $ 823,950 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Emerging & Other ​ ​ ​ Subscription revenue ​ $ 303,482 ​ $ 194,362 ​ $ 102,592 Marketplace revenue ​ 138,726 ​ 38,950 ​ 19,665 Advertising revenue: ​ ​ ​ Non-Google advertising revenue ​ 16,236 ​ 23,372 ​ 64,319 Google advertising revenue ​ 3,130 ​ 4,486 ​ 14,393 Total advertising revenue ​ 19,366 ​ 27,858 ​ 78,712 Service revenue ​ 4,410 ​ 3,881 ​ 22,142 Media production and distribution revenue ​ 3,585 ​ 8,897 ​ 61,717 Other revenue ​ 190 ​ 159 ​ 1,758 Total Emerging & Other revenue ​ $ 469,759 ​ $ 274,107 ​ $ 286,586
Schedule of Reconciliation of Adjusted EBITDA to Operating Income (Loss)	The following tables present operating income (loss) and Adjusted EBITDA by reportable segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Operating (loss) income: ​ ​ ​ ANGI Homeservices ​ $ (6,368) ​ $ 38,645 ​ $ 63,906 Vimeo ​ (26,392) ​ (51,921) ​ (35,594) Dotdash ​ 50,241 ​ 29,021 ​ 18,778 Search ​ (248,711) ​ 122,347 ​ 151,425 Emerging & Other ​ (70,896) ​ (21,790) ​ (26,627) Corporate ​ (270,223) ​ (166,751) ​ (136,053) Total ​ $ (572,349) ​ $ (50,449) ​ $ 35,835 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Adjusted EBITDA: (d) ​ ​ ​ ANGI Homeservices ​ $ 172,804 ​ $ 202,297 ​ $ 247,506 Vimeo ​ $ (11,187) ​ $ (41,790) ​ $ (28,045) Dotdash ​ $ 66,206 ​ $ 39,601 ​ $ 21,384 Search ​ $ 51,344 ​ $ 124,163 ​ $ 182,905 Emerging & Other ​ $ (37,699) ​ $ (28,368) ​ $ (14,889) Corporate ​ $ (147,502) ​ $ (88,617) ​ $ (74,011) (d) The Company’s primary financial measure is Adjusted EBITDA, which is defined as operating income excluding: (1) stock-based compensation expense; (2) depreciation; and (3) acquisition-related items consisting of (i) amortization of intangible assets and impairments of goodwill and intangible assets, if applicable, and (ii) gains and losses recognized on changes in the fair value of contingent consideration arrangements. The Company believes this measure is useful for analysts and investors as this measure allows a more meaningful comparison between the Company’s performance and that of its competitors. The above items are excluded from the Company’s Adjusted EBITDA measure because these items are non-cash in nature. Adjusted EBITDA has certain limitations because it excludes the impact of these expenses. The following tables reconcile operating (loss) income for the Company’s reportable segments and net earnings attributable to IAC shareholders to Adjusted EBITDA: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquisition- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ related Contingent ​ ​ ​ ​ ​ ​ ​ Operating Stock-Based ​ ​ ​ ​ Consideration ​ ​ ​ ​ ​ ​ (Loss) ​ Compensation ​ ​ ​ ​ Amortization ​ Fair Value ​ Goodwill ​ ​ ​ ​ ​ Income ​ Expense ​ Depreciation ​ of Intangibles ​ Adjustments ​ Impairment ​ Adjusted EBITDA ​ ​ (In thousands) ANGI Homeservices ​ $ (6,368) ​ $ 83,649 ​ $ 52,621 ​ $ 42,902 ​ $ — ​ $ — ​ $ 172,804 Vimeo ​ (26,392) ​ $ — ​ $ 460 ​ $ 14,745 ​ $ — ​ $ — ​ $ (11,187) Dotdash ​ 50,241 ​ $ — ​ $ 1,794 ​ $ 14,171 ​ $ — ​ $ — ​ $ 66,206 Search ​ (248,711) ​ $ — ​ $ 2,709 ​ $ 32,200 ​ $ — ​ $ 265,146 ​ $ 51,344 Emerging & Other ​ (70,896) ​ $ 100 ​ $ 2,449 ​ $ 37,566 ​ $ (6,918) ​ $ — ​ $ (37,699) Corporate ​ (270,223) ​ $ 113,471 ​ $ 9,250 ​ $ — ​ $ — ​ $ — ​ $ (147,502) Total ​ (572,349) ​ ​ ​ ​ ​ ​ Interest expense ​ (16,166) ​ ​ ​ ​ ​ ​ Unrealized gain on investment in MGM Resorts International ​ 840,550 ​ ​ ​ ​ ​ ​ Other expense, net ​ (42,468) ​ ​ ​ ​ ​ ​ Earnings before income taxes ​ 209,567 ​ ​ ​ ​ ​ ​ Income tax benefit ​ 59,019 ​ ​ ​ ​ ​ ​ Net earnings ​ 268,586 ​ ​ ​ ​ ​ ​ Net loss attributable to noncontrolling interests ​ 1,140 ​ ​ ​ ​ ​ ​ Net earnings attributable to IAC shareholders ​ $ 269,726 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquisition- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ related Contingent ​ ​ ​ ​ ​ ​ ​ Operating Stock-based ​ ​ ​ ​ Consideration ​ ​ ​ ​ ​ ​ Income ​ Compensation ​ ​ ​ ​ Amortization ​ Fair Value ​ Goodwill ​ Adjusted ​ ​ (Loss) ​ Expense ​ Depreciation ​ of Intangibles ​ Arrangements ​ Impairment ​ EBITDA ​ ​ (In thousands) ANGI Homeservices ​ $ 38,645 ​ $ 68,255 ​ $ 39,915 ​ $ 55,482 ​ $ — ​ $ — ​ $ 202,297 Vimeo ​ ​ (51,921) ​ $ — ​ $ 478 ​ $ 9,653 ​ $ — ​ $ — ​ $ (41,790) Dotdash ​ 29,021 ​ $ — ​ $ 974 ​ $ 9,606 ​ $ — ​ $ — ​ $ 39,601 Search ​ 122,347 ​ $ — ​ $ 1,816 ​ $ — ​ $ — ​ $ — ​ $ 124,163 Emerging & Other ​ (21,790) ​ $ — ​ $ 715 ​ $ 9,127 ​ $ (19,738) ​ $ 3,318 ​ $ (28,368) Corporate ​ (166,751) ​ $ 66,083 ​ $ 12,051 ​ $ — ​ $ — ​ $ — ​ $ (88,617) Total ​ (50,449) ​ ​ ​ ​ ​ ​ Interest expense ​ (11,904) ​ ​ ​ ​ ​ ​ Other income, net ​ 34,047 ​ ​ ​ ​ ​ ​ Loss before income taxes ​ (28,306) ​ ​ ​ ​ ​ ​ Income tax benefit ​ 60,489 ​ ​ ​ ​ ​ ​ Net earnings ​ 32,183 ​ ​ ​ ​ ​ ​ Net earnings attributable to noncontrolling interests ​ (9,288) ​ ​ ​ ​ ​ ​ Net earnings attributable to IAC shareholders ​ $ 22,895 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquisition- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ related Contingent ​ ​ ​ ​ Operating ​ Stock-Based ​ ​ ​ ​ Consideration ​ ​ ​ ​ Income ​ Compensation ​ ​ ​ ​ Amortization ​ Fair Value ​ ​ ​ ​ ​ (Loss) Expense ​ Depreciation ​ of Intangibles ​ Adjustments ​ Adjusted EBITDA ​ ​ (In thousands) ANGI Homeservices ​ $ 63,906 ​ $ 97,078 ​ $ 24,310 ​ $ 62,212 ​ $ — ​ $ 247,506 Vimeo ​ (35,594) ​ $ — ​ $ 1,200 ​ $ 6,349 ​ $ — ​ $ (28,045) Dotdash ​ 18,778 ​ $ — ​ $ 969 ​ $ 1,637 ​ $ — ​ $ 21,384 Search ​ 151,425 ​ $ — ​ $ 3,311 ​ $ 28,169 ​ $ — ​ $ 182,905 Emerging & Other ​ (26,627) ​ $ 919 ​ $ 969 ​ $ 8,714 ​ $ 1,136 ​ $ (14,889) Corporate ​ (136,053) ​ $ 50,408 ​ $ 11,634 ​ $ — ​ $ — ​ $ (74,011) Total ​ 35,835 ​ ​ ​ ​ ​ Interest expense ​ (13,059) ​ ​ ​ ​ ​ Other income, net ​ 282,795 ​ ​ ​ ​ ​ Earnings before income taxes ​ 305,571 ​ ​ ​ ​ ​ Income tax provision ​ (13,200) ​ ​ ​ ​ ​ Net earnings ​ 292,371 ​ ​ ​ ​ ​ Net earnings attributable to noncontrolling interests ​ (45,599) ​ ​ ​ ​ ​ Net earnings attributable to IAC shareholders ​ $ 246,772 ​ ​ ​ ​ ​
Schedule of Capital Expenditures by Segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Capital expenditures: ​ ​ ​ ANGI Homeservices ​ $ 52,488 ​ $ 68,804 ​ $ 46,976 Vimeo ​ 844 ​ 2,801 ​ 209 Dotdash ​ 5,445 ​ — ​ 102 Search ​ 47 ​ 43 ​ 479 Emerging & Other ​ 1,363 ​ 387 ​ 751 Corporate ​ 1,383 ​ 25,863 ​ 6,163 Total ​ $ 61,570 ​ $ 97,898 ​ $ 54,680

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Supplemental Balance Sheet Information of Leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Leases Balance Sheet Classification 2020 2019 ​ ​ ​ ​ (In thousands) Assets: ​ ​ Right-of-use assets Other non-current assets ​ $ 171,741 ​ $ 138,608 ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ Current lease liabilities Accrued expenses and other current liabilities ​ $ 27,785 ​ $ 23,188 Long-term lease liabilities Other long-term liabilities ​ 206,389 ​ 168,321 Total lease liabilities ​ $ 234,174 ​ $ 191,509
Schedule of Lease Cost and Other Information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Lease Expense Income Statement Classification 2020 2019 ​ ​ ​ ​ (In thousands) Fixed lease expense Cost of revenue ​ $ 2,214 ​ $ 547 Fixed lease expense Selling and marketing expense ​ 12,779 ​ 10,613 Fixed lease expense General and administrative expense ​ 21,433 ​ 17,751 Fixed lease expense Product development expense ​ 3,456 ​ 1,502 Total fixed lease expense (a) ​ 39,882 ​ 30,413 Variable lease expense Cost of revenue ​ — ​ 83 Variable lease expense Selling and marketing expense ​ 2,314 ​ 1,573 Variable lease expense General and administrative expense ​ 7,452 ​ 5,729 Variable lease expense Product development expense ​ 939 ​ 391 Total variable lease expense ​ 10,705 ​ 7,776 Net lease expense ​ $ 50,587 ​ $ 38,189
Schedule of Maturities of Operating Lease Liabilities	Maturities of lease liabilities as of December 31, 2020 (b) ​ ​ ​ ​ ​ Years Ended December 31, In thousands 2021 ​ $ 38,664 2022 ​ ​ 38,473 2023 ​ 36,648 2024 ​ 35,106 2025 ​ 26,841 Thereafter ​ 227,409 Total ​ 403,141 Less: Interest ​ 168,967 Present value of lease liabilities ​ $ 234,174 (b) Lease payments exclude $0.1 million of legally binding minimum lease payments for leases signed but not yet commenced.
Schedule of Weighted-Average Lease Term and Discount Rate of Leases	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Remaining lease term 15.4 years 17.4 years ​ Discount rate 5.66 % 6.12 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Other Information: ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ $ 81,636 ​ $ 61,657 Cash paid for amounts included in the measurement of lease liabilities ​ $ 44,978 ​ $ 35,321

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of Commercial Commitments Outstanding	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of Commitment Expiration Per Period ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Less Than ​ 1-3 ​ 3-5 ​ More Than ​ Amounts ​ ​ 1 Year ​ Years ​ Years ​ 5 Years ​ Committed ​ (In thousands) Purchase obligations ​ $ 45,819 ​ $ 520 ​ $ — ​ $ — ​ $ 46,339

Related Party Disclosures (Tabl

Related Party Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months ​ ​ ​ ​ ​ ​ ​ ​ Ended June 30, ​ ​ ​ ​ ​ ​ ​ ​ the date of the ​ ​ ​ ​ ​ ​ ​ ​ MTCH Separation ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Cash transfers (from) to Old IAC related to its centrally managed U.S. treasury management function, acquisitions and cash expenses paid by Old IAC on behalf of the Company, net ​ $ (1,742,854) ​ $ (182,382) ​ $ 215,993 Contribution of buildings to Match Group ​ ​ 34,973 ​ ​ — ​ ​ — Taxes ​ 34,436 ​ (1,874) ​ 1,120 Allocation of costs from Old IAC ​ (12,652) ​ (80,143) ​ (71,977) Interest income, net ​ 102 ​ 420 ​ 325 Net (increase) decrease in Old IAC’s investment in the Company prior to the MTCH Separation ​ $ (1,685,995) ​ $ (263,979) ​ $ 145,461

FINANCIAL STATEMENT DETAILS (Ta

FINANCIAL STATEMENT DETAILS (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheet to the total amounts shown in the statement of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 December 31, 2018 December 31, 2017 ​ ​ (In thousands) Cash and cash equivalents ​ $ 3,476,188 ​ $ 839,796 ​ $ 884,975 ​ $ 757,202 Restricted cash included in other current assets ​ 473 ​ 527 ​ 1,441 ​ 2,737 Restricted cash included in other assets ​ 449 ​ 409 ​ 420 ​ — Total cash and cash equivalents and restricted cash as shown on the statement of cash flows ​ $ 3,477,110 ​ $ 840,732 ​ $ 886,836 ​ $ 759,939
Schedule of Restricted Cash	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 December 31, 2018 December 31, 2017 ​ ​ (In thousands) Cash and cash equivalents ​ $ 3,476,188 ​ $ 839,796 ​ $ 884,975 ​ $ 757,202 Restricted cash included in other current assets ​ 473 ​ 527 ​ 1,441 ​ 2,737 Restricted cash included in other assets ​ 449 ​ 409 ​ 420 ​ — Total cash and cash equivalents and restricted cash as shown on the statement of cash flows ​ $ 3,477,110 ​ $ 840,732 ​ $ 886,836 ​ $ 759,939
Schedule of Other Current Assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Other current assets: ​ ​ Capitalized costs to obtain a contract with a customer ​ $ 61,514 ​ $ 43,069 Prepaid expenses ​ 50,123 ​ 41,934 Capitalized downloadable search toolbar costs, net ​ 12,730 ​ 21,985 Other ​ 23,263 ​ 45,346 Other current assets ​ $ 147,630 ​ $ 152,334
Schedule of Property and Equipment, Net	​ ​ ​ ​ ​ Estimated Asset Category ​ Useful Lives Buildings and leasehold improvements 3 Capitalized software and computer equipment 2 Furniture and other equipment 3 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Building, capitalized software, leasehold improvements and equipment ​ ​ Buildings and leasehold improvements ​ $ 198,778 ​ $ 242,882 Capitalized software and computer equipment ​ 149,789 ​ 124,523 Furniture and other equipment ​ 84,161 ​ 84,640 Land ​ — ​ 11,591 Projects in progress ​ 53,635 ​ 43,576 Building, capitalized software, leasehold improvements and equipment ​ 486,363 ​ 507,212 Accumulated depreciation and amortization ​ (208,112) ​ (201,798) Building, capitalized software, leasehold improvements and equipment, net ​ $ 278,251 ​ $ 305,414
Schedule of Accrued Expenses and Other Current Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 ​ ​ (In thousands) Accrued expenses and other current liabilities: ​ ​ Accrued employee compensation and benefits ​ $ 126,161 ​ $ 105,960 Accrued advertising expense ​ 62,854 ​ 59,269 Accrued revenue share ​ 38,710 ​ 30,574 Other ​ 155,837 ​ 124,670 Accrued expenses and other current liabilities ​ $ 383,562 ​ $ 320,473
Schedule of Other (Expense) Income, Net	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Impairments related to COVID-19 (a) ​ $ (59,001) ​ $ — ​ $ — Realized gains related to the sale of investments ​ 10,661 ​ 2,327 ​ 589 Realized gains related to the sale of the investment in Pinterest ​ — ​ 20,486 ​ 26,777 Upward adjustments to the carrying value of equity securities without readily determinable fair values (b) ​ — ​ 18,505 ​ 128,901 Interest income ​ 7,189 ​ 15,164 ​ 9,125 Realized gains (losses) related to the sale of business (c) ​ 1,061 ​ (8,239) ​ 121,230 Unrealized reduction in the estimated fair value of a warrant ​ (1,213) ​ (9,123) ​ — Mark-to-market loss on an indemnification claim related to the Handy acquisition ​ (181) ​ (1,779) ​ — Other ​ (984) ​ (3,294) ​ (3,827) Other (expense) income, net ​ $ (42,468) ​ $ 34,047 ​ $ 282,795 (a) Includes $51.5 million in impairments related to investments in equity securities without readily determinable fair values and $7.5 million in impairments of a note receivable and a warrant related to certain investees in the year ended December 31, 2020. (b) Includes a $128.8 million unrealized gain to adjust the remaining interest in Pinterest to fair value in accordance with ASU No. 2016-02 in the year ended December 31, 2018. (c) Includes a realized loss on the sale of Vimeo’s hardware business, which was sold in the first quarter of 2019, and gains related to the sales of Dictionary.com, Electus, Felix and CityGrid in the year ended December 31, 2018.
Schedule of Supplemental Disclosure of Cash Flow Information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 ​ ​ (In thousands) Cash paid (received) during the year for: ​ ​ ​ Interest ​ $ 6,524 ​ $ 10,042 ​ $ 13,108 Income tax payments ​ $ 6,876 ​ $ 4,861 ​ $ 4,084 Income tax refunds ​ $ (2,080) ​ $ (3,048) ​ $ (30,320)

QUARTERLY RESULTS (UNAUDITED) (

QUARTERLY RESULTS (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Results	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarter Ended Quarter Ended Quarter Ended Quarter Ended ​ ​ ​ March 31 (a)(e) ​ June 30 (b)(e) ​ September 30 (c)(e) ​ December 31 (d)(e) ​ ​ ​ (In thousands, except per share data) Year Ended December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenue ​ ​ $ 684,124 ​ $ 726,361 ​ $ 788,377 ​ $ 848,819 Cost of revenue ​ ​ $ 179,327 ​ $ 178,639 ​ $ 207,643 ​ $ 249,122 Operating loss ​ ​ $ (312,338) ​ $ (107,019) ​ $ (128,626) ​ $ (24,366) Net (loss) earnings ​ ​ $ (330,571) ​ $ (94,064) ​ $ 185,861 ​ $ 507,360 Net (loss) earnings attributable to IAC shareholders ​ ​ $ (328,199) ​ $ (96,117) ​ $ 184,917 ​ $ 509,125 Per share information attributable to IAC shareholders: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic (loss) earnings per share (f)(g) ​ ​ $ (3.86) ​ $ (1.13) ​ $ 2.17 ​ $ 5.96 Diluted (loss) earnings per share (f)(g) ​ ​ $ (3.86) ​ $ (1.13) ​ $ 2.04 ​ $ 5.59 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarter Ended Quarter Ended Quarter Ended Quarter Ended ​ ​ March 31 (e) ​ June 30 (e) ​ September 30 (e) ​ December 31 (e) ​ ​ (In thousands, except per share data) Year Ended December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ Revenue ​ $ 641,220 ​ $ 688,685 ​ $ 705,382 ​ $ 670,514 Cost of revenue ​ $ 139,848 ​ $ 149,725 ​ $ 158,161 ​ $ 152,506 Operating (loss) income ​ $ (34,183) ​ $ (13,770) ​ $ 13,912 ​ $ (16,408) Net (loss) earnings ​ $ (13,673) ​ $ 22,021 ​ $ 18,378 ​ $ 5,457 Net (loss) earnings attributable to IAC shareholders ​ $ (14,247) ​ $ 13,789 ​ $ 16,466 ​ $ 6,887 Per share information attributable to IAC shareholders: ​ ​ ​ ​ Basic (loss) earnings per share (f)(g) ​ $ (0.17) ​ $ 0.16 ​ $ 0.19 ​ $ 0.08 Diluted (loss) earnings per share (f)(g) ​ $ (0.17) ​ $ 0.16 ​ $ 0.19 ​ $ 0.08 (a) The first quarter of 2020 includes: i. as a result of the effects of COVID-19: ● an after-tax $208.9 million impairment related to the goodwill of the Desktop reporting unit; ● an after-tax $16.4 million impairment related to certain indefinite-lived intangible assets of the Desktop reporting unit; ● an after-tax $51.5 million impairment of certain equity securities without readily determinable fair values; and ● an after-tax $7.5 million impairment of a note receivable and a warrant related to certain investee. (b) The second quarter includes: i. after-tax stock-based compensation expense of $40.7 million related to the modification of previously issued equity awards as a result of the MTCH Separation; and an ii. after-tax unrealized loss of $24.7 million related to IAC’s investment in MGM. (c) The third quarter of 2020 includes: i. an after-tax $53.2 million impairment related to the goodwill of the Desktop reporting unit; ii. an after-tax $8.3 million impairment of intangible assets of the Desktop reporting unit; and an iii. after-tax unrealized gain of $227.7 million related to IAC’s investment in MGM. (d) The fourth quarter of 2020 includes after-tax unrealized gain of $439.6 million related to IAC’s investment in MGM. (e) The first, second, third and fourth quarters of 2020 include after-tax stock-based compensation expense of $8.9 million, $2.7 million, $4.1 million and $1.5 million, respectively, related to the modification of previously issued HomeAdvisor equity awards and previously issued Angie’s List equity awards, both of which were converted into ANGI Homeservices’ equity awards in the Combination. The first, second, third and fourth quarters of 2019 include after-tax stock-based compensation expense of $7.4 million, $6.3 million, $5.7 million, and $5.7 million, respectively, related to this modification. (f) Quarterly per share amounts may not add to the related annual per share amount because of differences in the average common shares outstanding during each period. (g) The Company computed basic and diluted earnings per share for periods prior to the MTCH Separation using the shares issued on June 30, 2020 in connection with the MTCH Separation.

ORGANIZATION - Narrative (Detai

ORGANIZATION - Narrative (Details) item in Thousands, project in Millions	12 Months Ended
	Dec. 31, 2020categoryitemproject
Noncontrolling Interest [Line Items]
Number of service categories | category	500
Number of service professionals | item	240
Number of projects | project	32
ANGI Homeservices
Noncontrolling Interest [Line Items]
Ownership interest (as a percent)	84.30%
Voting interest (as a percent)	98.20%
Vimeo
Noncontrolling Interest [Line Items]
Ownership interest (as a percent)	93.20%
Vimeo | Common Stock
Noncontrolling Interest [Line Items]
Ownership interest (as a percent)	89.70%
Vimeo | Class B Common Stock
Noncontrolling Interest [Line Items]
Ownership interest (as a percent)	97.60%

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	Jan. 01, 2018USD ($)	Dec. 31, 2020USD ($)item	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)item	Dec. 31, 2019USD ($)item	Dec. 31, 2018USD ($)item	Oct. 01, 2018USD ($)
Intangible Assets and Goodwill
Goodwill Impairment										$ 265,146,000	$ 3,318,000	$ 0
Impairment of equity securities without readily determinable fair value		$ 51,500,000			$ 51,500,000					51,500,000
Impairment of note receivable and warrant					7,500,000					$ 7,500,000
Number of equity method investments | item		1								1
Equity method investment		$ 1,152,000				$ 0				$ 1,152,000	0
Retained earnings		694,042,000				0				694,042,000	0
Deferred income taxes		52,593,000				44,459,000				52,593,000	44,459,000
Increase (decrease) in deferred revenue										81,431,000	28,136,000	36,409,000
Amortization of capitalized contract costs										109,000,000	99,800,000	70,600,000
Current capitalized contract costs	$ 40,600,000	61,514,000				43,069,000				61,514,000	43,069,000
Non-current capitalized contract costs	4,500,000	9,300,000				6,200,000				$ 9,300,000	6,200,000
Period of payment due from customers for accounts receivable										30 days
Current deferred revenue		275,093,000				178,647,000				$ 275,093,000	178,647,000	150,100,000
Non-current deferred revenue		1,500,000				1,300,000				1,500,000	1,300,000	1,700,000
Deferred revenue recognized during period										$ 170,700,000	146,500,000
Maturity period at purchase (less than)										91 days
Marketable debt securities						0					0
Revenue		848,819,000	$ 788,377,000	$ 726,361,000	684,124,000	670,514,000	$ 705,382,000	$ 688,685,000	$ 641,220,000	$ 3,047,681,000	2,705,801,000	2,533,048,000
Accounts receivable, net of allowance and reserves		270,453,000				181,875,000				270,453,000	181,875,000
Building, capitalized software, leasehold improvements and equipment, net		278,251,000				305,414,000				278,251,000	305,414,000
Goodwill		1,879,438,000				1,616,867,000				1,879,438,000	1,616,867,000	1,484,117,000
Intangible assets, net of accumulated amortization		405,840,000				350,150,000				405,840,000	350,150,000
Advertising expense										$ 862,200,000	$ 855,200,000	$ 798,100,000
Estimated weighted-average useful life (in months)										18 months
Put and call arrangements exercised | item										1	1	2
Accounting Standards Update 2014-09
Intangible Assets and Goodwill
Retained earnings	40,300,000
United States
Intangible Assets and Goodwill
Building, capitalized software, leasehold improvements and equipment, net		266,169,000				297,433,000				$ 266,169,000	$ 297,433,000
Foreign Currency Translation Adjustment | Other (Expense) Income, Net
Intangible Assets and Goodwill
Gains (losses) reclassified to earnings										100,000	0	$ (100,000)
Redeemable Noncontrolling Interest
Intangible Assets and Goodwill
Purchase of noncontrolling interests										183,300,000	11,600,000	$ 6,600,000
Software and software development costs
Intangible Assets and Goodwill
Building, capitalized software, leasehold improvements and equipment, net		68,000,000				56,300,000				$ 68,000,000	$ 56,300,000
Revenue | Customer Concentration Risk
Intangible Assets and Goodwill
Concentration risk (as a percent)										16.00%	25.00%	30.00%
Revenue										$ 498,300,000	$ 677,000,000	$ 765,600,000
Revenue Benchmark | Geographic Concentration Risk | United States
Intangible Assets and Goodwill
Concentration risk (as a percent)										80.00%
Google Inc.
Intangible Assets and Goodwill
Accounts receivable, net of allowance and reserves		61,900,000				$ 53,000,000				$ 61,900,000	$ 53,000,000
Google Inc. | Revenue | Customer Concentration Risk
Intangible Assets and Goodwill
Concentration risk (as a percent)										18.00%	27.00%	33.00%
Mosaic Group | Desktop
Intangible Assets and Goodwill
Goodwill		$ 759,500,000								$ 759,500,000
Handy Technologies, Inc. | Revenue Change
Intangible Assets and Goodwill
Revenue										$ 73,800,000
Desktop | Trade names
Intangible Assets and Goodwill
Impairment charges on indefinite-lived intangible assets												$ 27,700,000
College Humor Media
Intangible Assets and Goodwill
Goodwill Impairment											$ 3,300,000
College Humor Media | Trade names
Intangible Assets and Goodwill
Impairment charges on indefinite-lived intangible assets											$ 700,000	1,100,000
Maximum | Discount Rate | Indefinite-lived Intangible Assets
Intangible Assets and Goodwill
Measurement input (as a percent)		0.250				0.275				0.250	0.275
Maximum | Royalty Rate | Indefinite-lived Intangible Assets
Intangible Assets and Goodwill
Measurement input (as a percent)		0.055								0.055
Minimum | Discount Rate | Indefinite-lived Intangible Assets
Intangible Assets and Goodwill
Measurement input (as a percent)		0.115				0.115				0.115	0.115
Minimum | Royalty Rate | Indefinite-lived Intangible Assets
Intangible Assets and Goodwill
Measurement input (as a percent)		0.010								0.010
Minimum | Mosaic Group | Discount Rate
Intangible Assets and Goodwill
Measurement input (as a percent)		0.150								0.150
Minimum | Desktop | Discount Rate
Intangible Assets and Goodwill
Measurement input (as a percent)						0.125					0.125
ANGI Homeservices
Intangible Assets and Goodwill
Goodwill Impairment										$ 0	$ 0
Period of membership subscription										1 year
Market capitalization													$ 5,500,000,000
Amount by which market capitalization exceeds carrying value													$ 4,300,000,000
Goodwill		$ 892,133,000				$ 884,296,000				$ 892,133,000	884,296,000	895,071,000
ANGI Homeservices | Accounting Standards Update 2014-09
Intangible Assets and Goodwill
Retained earnings	25,900,000
Deferred income taxes	8,000,000
Current capitalized contract costs	29,700,000
Non-current capitalized contract costs	4,200,000
ANGI Homeservices | Noncontrolling Interests | Accounting Standards Update 2014-09
Intangible Assets and Goodwill
Retained earnings	3,400,000
ANGI Homeservices | Operating Segments
Intangible Assets and Goodwill
Goodwill Impairment										0	0
Revenue										$ 1,467,925,000	1,326,205,000	1,132,241,000
ANGI Homeservices | Angie's List [Member]
Intangible Assets and Goodwill
Period of membership subscription										1 year
Vimeo | Operating Segments
Intangible Assets and Goodwill
Goodwill Impairment										$ 0	0
Revenue										$ 283,218,000	196,015,000	159,641,000
Vimeo | Maximum
Intangible Assets and Goodwill
Period of membership subscription										3 years
Vimeo | Minimum
Intangible Assets and Goodwill
Period of membership subscription										1 month
Publishing and Applications | Google Inc.
Intangible Assets and Goodwill
Revenue										$ 556,400,000	733,500,000	825,200,000
Dotdash | Operating Segments
Intangible Assets and Goodwill
Goodwill Impairment										0	0
Revenue										213,753,000	167,594,000	130,991,000
Search
Intangible Assets and Goodwill
Goodwill Impairment										265,146,000	0
Goodwill		$ 0				$ 265,146,000				0	265,146,000	265,146,000
Search | Accounting Standards Update 2014-09
Intangible Assets and Goodwill
Retained earnings	15,500,000
Deferred income taxes	4,900,000
Increase (decrease) in deferred revenue	$ (20,300,000)
Search | Operating Segments
Intangible Assets and Goodwill
Goodwill Impairment										265,146,000	0
Revenue										613,274,000	742,184,000	823,950,000
Search | Ask Media Group | Google Inc. | Revenue | Customer Concentration Risk
Intangible Assets and Goodwill
Revenue										344,800,000	385,900,000	339,000,000
Search | Desktop
Intangible Assets and Goodwill
Goodwill Impairment			53,200,000		212,000,000					265,100,000
Impairment charges on indefinite-lived intangible assets			$ 10,800,000		$ 21,400,000					32,200,000
Search | Desktop | Google Inc. | Revenue | Customer Concentration Risk
Intangible Assets and Goodwill
Revenue										$ 153,500,000	$ 291,100,000	$ 426,500,000
Search | Maximum | Desktop
Intangible Assets and Goodwill
Period of membership subscription										2 years
Search | Minimum | Desktop
Intangible Assets and Goodwill
Period of membership subscription										1 year

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowance for Credit Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at January 1	$ 20,257
Provision for credit losses	80,765	$ 65,723	$ 48,362
Write-offs charged against the allowance	(75,815)
Recoveries collected	2,447
Balance at December 31	27,654	20,257
Revenue reserve	2,100	3,900
Allowance for credit loss, current and revenue reserve	$ 29,700	$ 24,100

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Buildings and leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	3 years
Buildings and leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	39 years
Capitalized software and computer equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	2 years
Capitalized software and computer equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	3 years
Furniture and other equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	3 years
Furniture and other equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	12 years

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Income tax benefit related to net operating loss carryforwards	$ 240,300
Income tax expense (benefit) related to operating loss carryforwards recorded as reduction to goodwill	32,100
Deferred tax assets, gross	611,983	$ 378,834
Tax credit carryforwards	66,200
Tax credit carryforwards that can be carried forward indefinitely	11,500
Tax credit carryforwards expiring primarily by 2018 and 2037	54,700
Valuation Allowance
Decrease in valuation allowance	20,700
Valuation allowance at end of period	113,700
Income Taxes Paid, Net [Abstract]
Unrecognized tax benefits, income tax penalties and interest accrued	22,100	20,300
Tax positions for which the ultimate deductibility is highly certain but timing is uncertain	20,400	18,900
Change in unrecognized tax benefits unrelated to Federal income taxes statute of limitations expiring within twelve months of current reporting period	6,100
Federal Tax Authority
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Net operating loss carryforwards	1,300,000
Net operating loss carryforwards not subject to expiration	843,500
Net operating loss carryforwards without restrictions	833,300
Net operating loss carryforwards subject to expiration within 20 years	484,100
State Tax Authority
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Net operating loss carryforwards	840,400
Net operating loss carryforwards without restrictions	543,800
Tax credit carryforwards	1,900
Foreign Tax Authority
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Net operating loss carryforwards	442,200
Net operating loss carryforwards not subject to expiration	401,800
Net operating loss carryforwards subject to expiration within 20 years	40,400
Tax credit carryforwards	12,700
Tax credit carryforwards related to research and development	51,600
Federal and State Tax Credits
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Deferred tax assets, gross	$ 489,800
Continuing Operations
Income Taxes Paid, Net [Abstract]
Unrecognized tax benefits including tax interest accrued from Old IAC		$ 11,600

INCOME TAXES - Income before In

INCOME TAXES - Income before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S.	$ 197,545	$ (74,360)	$ 269,267
Foreign	12,022	46,054	36,304
Earnings (loss) before income taxes	$ 209,567	$ (28,306)	$ 305,571

INCOME TAXES - Components of In

INCOME TAXES - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current income tax (benefit) provision:
Federal	$ (29,176)	$ (1,117)	$ (1,187)
State	2,253	197	1,514
Foreign	(176)	3,201	4,108
Current income tax (benefit) provision	(27,099)	2,281	4,435
Deferred income tax (benefit) provision:
Federal	(20,054)	(51,952)	20,156
State	(7,726)	(10,645)	(7,272)
Foreign	(4,140)	(173)	(4,119)
Deferred income tax (benefit) provision	(31,920)	(62,770)	8,765
Income tax (benefit) provision	$ (59,019)	$ (60,489)	$ 13,200

INCOME TAXES - Deferred Tax Ass

INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 404,807	$ 201,766
Stock-based compensation	44,926	62,566
Long-term lease liabilities	58,800	42,486
Tax credit carryforwards	48,936	38,066
Accrued expenses	20,490	12,911
Other	34,024	21,039
Total deferred tax assets	611,983	378,834
Less: valuation allowance	(113,684)	(92,990)
Net deferred tax assets	498,299	285,844
Deferred tax liabilities:
Investment in subsidiaries	(242,537)	(240,420)
Investment in MGM Resorts International	(197,998)
Right-of-use assets	(43,418)	(29,654)
Intangible assets	(30,094)	(28,488)
Other	(34,639)	(31,534)
Total deferred tax liabilities	(548,686)	(330,096)
Net deferred tax liabilities	$ (50,387)	$ (44,252)

INCOME TAXES - Effective Income

INCOME TAXES - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax provision (benefit) at the federal statutory rate of 21%	$ 44,009	$ (5,944)	$ 64,170
State income taxes, net of effect of federal tax benefit	15,936	(277)	5,188
Stock-based compensation	(167,998)	(56,871)	(39,326)
Non-deductible goodwill impairment	53,012	0	0
Non-deductible executive compensation	14,219	7,409	2,983
Change in valuation allowance on capital losses	11,385	(5,815)	(1,280)
Research credit	(7,407)	(5,105)	(3,167)
Amortizable tax basis related to intercompany transaction	(7,044)	0	0
Non-deductible expenses	6,556	5,460	1,727
Change in judgement on beginning of the year valuation allowance	(3,544)
Net adjustment related to the reconciliation of income tax provision accruals to tax returns	(2,591)	138	42
Deferred tax adjustment for enacted changes in tax laws and rates	(14,579)	(687)	(13,646)
Other, net	(973)	1,203	(3,491)
Income tax (benefit) provision	$ (59,019)	$ (60,489)	$ 13,200

INCOME TAXES - Income Tax Conti

INCOME TAXES - Income Tax Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning of the period	$ 18,060	$ 15,451	$ 14,528
Additions based on tax positions related to the current year	3,977	2,781	1,455
Settlements	(4,309)
Additions for tax positions of prior years	2,781	238	235
Additions for tax positions of prior years	(351)	(410)	(767)
Balance at end of the period	$ 20,158	$ 18,060	$ 15,451

BUSINESS COMBINATION - Narrativ

BUSINESS COMBINATION - Narrative (Details) - USD ($) $ in Millions	Feb. 11, 2020	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Care.com
Business Acquisition [Line Items]
Proportion of voting interests acquired (as a percent)	100.00%
Total purchase price	$ 626.9
Cash acquisition price	587
Consideration transferred, equity interests	$ 40
Deferred tax assets, adjustment		$ 32.1
Goodwill adjustment		$ 32.1
Revenue			$ 182.4
Net earnings (loss)			(31.4)
Write-off due to deferred revenue			17.3
Business Combination, Acquisition Related Costs			16.7
Deferred Revenue Write Off Adjustment
Business Acquisition [Line Items]
Adjustment to increase (decrease) in revenues			17.1	$ (11.1)
Amortization Adjustment
Business Acquisition [Line Items]
Adjustment to decrease in amortization of intangible assets				$ 25.9
One-Time Acquisition-related Costs
Business Acquisition [Line Items]
Adjustment to increase (decrease) in revenues			$ (72.8)

BUSINESS COMBINATION - Prelimin

BUSINESS COMBINATION - Preliminary Estimated Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Feb. 11, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,879,438		$ 1,616,867	$ 1,484,117
Care.com
Business Acquisition [Line Items]
Cash and cash equivalents		$ 57,702
Short-term investments		20,000
Accounts receivable		20,213
Other current assets		7,479
Property and equipment		2,894
Goodwill		404,313
Intangible assets		116,800
Deferred income taxes		32,112
Other non-current assets		30,444
Total assets		691,957
Deferred revenue		(13,422)
Other current liabilities		(39,698)
Deferred income taxes		(25,824)
Other non-current liabilities		(26,039)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net, Total		$ 586,974

BUSINESS COMBINATION - Prelim_2

BUSINESS COMBINATION - Preliminary Estimated Fair Value of Intangible Assets Acquired (Details) - USD ($) $ in Thousands	Feb. 11, 2020	Dec. 31, 2020
Acquired Intangible Assets [Line Items]
Useful Life (Years)		18 months
Care.com
Acquired Intangible Assets [Line Items]
Total identifiable intangible assets acquired	$ 116,800
Care.com | Developed technology
Acquired Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 21,200
Useful Life (Years)	2 years
Care.com | Customer relationships
Acquired Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 35,500
Care.com | Customer relationships | Minimum
Acquired Intangible Assets [Line Items]
Useful Life (Years)	2 years
Care.com | Customer relationships | Maximum
Acquired Intangible Assets [Line Items]
Useful Life (Years)	5 years
Care.com | Provider relationships
Acquired Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 800
Useful Life (Years)	4 years
Care.com | Indefinite-lived trade name and trademarks
Acquired Intangible Assets [Line Items]
Indefinite-lived trade name and trademarks	$ 59,300

BUSINESS COMBINATION - Pro-Form

BUSINESS COMBINATION - Pro-Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition, Pro Forma Information [Abstract]
Revenue	$ 3,090,779	$ 2,904,243
Net earnings (loss) attributable to IAC shareholders	$ 296,933	$ (16,926)
Basic earnings (loss) per share attributable to ANGI Homeservices Inc. shareholders (USD per share)	$ 3.48	$ (0.20)
Diluted earnings (loss) per share attributable to ANGI Homeservices Inc. shareholders (USD per share)	$ 3.26	$ (0.20)

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 1,879,438	$ 1,616,867	$ 1,484,117
Intangible assets with indefinite lives	246,913	225,296
Intangible assets with definite lives, net of accumulated amortization	158,927	124,854
Total goodwill and intangible assets, net	$ 2,285,278	$ 1,967,017

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Goodwill by Reporting Unit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill
Balance at beginning of period	$ 1,616,867	$ 1,484,117
Additions	522,070	165,313
(Deductions)	(38)	(29,293)
Impairment	(265,146)	(3,318)	$ 0
Foreign Exchange Translation	5,685	48
Balance at end of period	1,879,438	1,616,867	1,484,117
ANGI Homeservices
Goodwill
Balance at beginning of period	884,296	895,071
Additions	2,665	18,326
(Deductions)	0	(29,293)
Impairment	0	0
Foreign Exchange Translation	5,172	192
Balance at end of period	892,133	884,296	895,071
Vimeo
Goodwill
Balance at beginning of period	219,374	77,152
Additions	0	142,222
(Deductions)	(38)	0
Impairment	0	0
Foreign Exchange Translation	0	0
Balance at end of period	219,336	219,374	77,152
Search
Goodwill
Balance at beginning of period	265,146	265,146
Additions	0	0
(Deductions)	0	0
Impairment	(265,146)	0
Foreign Exchange Translation	0	0
Balance at end of period	0	265,146	265,146
Emerging & Other
Goodwill
Balance at beginning of period	248,051	246,748
Additions	519,405	4,765
(Deductions)	0	0
Impairment	0	(3,318)
Foreign Exchange Translation	513	(144)
Balance at end of period	$ 767,969	$ 248,051	$ 246,748

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill impairment				$ 265,146	$ 3,318	$ 0
College Humor Media
Goodwill [Line Items]
Goodwill impairment					3,300
Search
Goodwill [Line Items]
Goodwill impairment				265,146	0
Goodwill, impaired, accumulated impairment loss			$ 716,200	981,300	716,200
Search | Desktop
Goodwill [Line Items]
Goodwill impairment	$ 53,200	$ 212,000		265,100
Impairment charges on indefinite-lived intangible assets	$ 10,800	$ 21,400		32,200
Emerging & Other
Goodwill [Line Items]
Goodwill impairment				0	3,318
Emerging & Other | College Humor Media
Goodwill [Line Items]
Goodwill impairment			3,300
Goodwill, impaired, accumulated impairment loss			14,900		14,900
Dotdash
Goodwill [Line Items]
Goodwill, impaired, accumulated impairment loss			$ 198,300	$ 198,300	$ 198,300

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Intangible Assets with Definite Lives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible assets with definite lives
Gross Carrying Amount	$ 437,566	$ 326,308
Accumulated Amortization	(278,639)	(201,454)
Total	$ 158,927	$ 124,854
Weighted-Average Useful Life (Years)	4 years 1 month 6 days	3 years 8 months 12 days
Technology
Intangible assets with definite lives
Gross Carrying Amount	$ 167,997	$ 143,255
Accumulated Amortization	(102,355)	(73,483)
Total	$ 65,642	$ 69,772
Weighted-Average Useful Life (Years)	4 years 1 month 6 days	4 years 6 months
Service professional relationships
Intangible assets with definite lives
Gross Carrying Amount	$ 97,960	$ 99,651
Accumulated Amortization	(97,312)	(76,445)
Total	$ 648	$ 23,206
Weighted-Average Useful Life (Years)	3 years	2 years 10 months 24 days
Provider relationships
Intangible assets with definite lives
Gross Carrying Amount	$ 91,887	$ 44,286
Accumulated Amortization	(33,864)	(24,226)
Total	$ 58,023	$ 20,060
Weighted-Average Useful Life (Years)	4 years	3 years 3 months 18 days
Trade names
Intangible assets with definite lives
Gross Carrying Amount	$ 53,383	$ 12,777
Accumulated Amortization	(19,227)	(8,082)
Total	$ 34,156	$ 4,695
Weighted-Average Useful Life (Years)	6 years 7 months 6 days	3 years 6 months
Memberships
Intangible assets with definite lives
Gross Carrying Amount	$ 15,900	$ 15,900
Accumulated Amortization	$ (15,900)	(11,940)
Total		$ 3,960
Weighted-Average Useful Life (Years)	3 years	3 years
Other
Intangible assets with definite lives
Gross Carrying Amount	$ 10,439	$ 10,439
Accumulated Amortization	(9,981)	(7,278)
Total	$ 458	$ 3,161
Weighted-Average Useful Life (Years)	3 years 4 months 24 days	3 years 4 months 24 days

GOODWILL AND INTANGIBLE ASSET_6

GOODWILL AND INTANGIBLE ASSETS - Expected Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 62,600
2022	37,982
2023	23,209
2024	11,292
2025	9,040
Thereafter	14,804
Total	$ 158,927	$ 124,854

FINANCIAL INSTRUMENTS AND FAI_3

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Current Available-for-Sale Marketable Securities (Details) $ in Thousands	Dec. 31, 2020USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 224,976
Gross Unrealized Gains	3
Gross Unrealized Losses	0
Fair Value	224,979
Treasury discount notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	224,976
Gross Unrealized Gains	3
Gross Unrealized Losses	0
Fair Value	$ 224,979

FINANCIAL INSTRUMENTS AND FAI_4

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($) shares in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Mar. 31, 2020	Feb. 11, 2020	Dec. 31, 2019	Sep. 30, 2019
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Marketable debt securities	$ 224,979,000	$ 224,979,000			$ 0
Contractual maturity of current available-for-sale debt securities		1 year
Available-for-sale marketable debt securities in a continuous unrealized loss position for longer than twelve months	0	$ 0
Impairment of equity securities without readily determinable fair value	51,500,000	51,500,000	$ 51,500,000
Upward adjustments to the carrying value of equity securities without readily determinable fair values	19,700,000	19,700,000
Downward adjustments to equity securities without readily determinable fair value	43,500,000	43,500,000
Equity method investment	1,152,000	1,152,000			0
Contingent consideration arrangements, range of outcomes, value, high	15,000,000	15,000,000
Contingent consideration arrangement	$ 0	$ 0			6,918,000
Non-current portion of contingent consideration arrangement liability					$ 6,900,000
Turo
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Ownership interest (as a percent)	26.80%	26.80%
Care.com
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration arrangement				$ 1,000,000
Turo
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Method Investment, Number of Shares Acquired	0.3
Equity method investment	$ 1,100,000	$ 1,100,000				$ 250,000,000
MGM
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities, FV-NI, Number of Shares Purchased		59

FINANCIAL INSTRUMENTS AND FAI_5

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - MGM Investment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Long-term investments	$ 297,643	$ 347,975
MGM
Schedule of Investments [Line Items]
Long-term investments	$ 1,860,158	$ 0

FINANCIAL INSTRUMENTS AND FAI_6

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Long-Term Investments (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Equity securities without readily determinable fair values	$ 296,491,000	$ 347,975,000
Equity method investment	1,152,000	0
Total long-term investments	$ 297,643,000	$ 347,975,000

FINANCIAL INSTRUMENTS AND FAI_7

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Realized and Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Adjustments to Carrying Value of Equity Securities without Readily Determinable Fair Value [Abstract]
Upward adjustments (gross unrealized gains)	$ 0	$ 19,698
Downward adjustments including impairments (gross unrealized losses)	(51,484)	(1,193)
Total	(51,484)	18,505
Adjustments to Carrying Value of Non-Marketable Equity Securities [Abstract]
Realized gains, net, for equity securities sold	2,161	22,880	$ 27,366
Unrealized gains, net, on equity securities held	797,565	18,505	126,063
Total gains recognized, net	$ 799,726	$ 41,385	$ 153,429

FINANCIAL INSTRUMENTS AND FAI_8

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities:		$ 0
Investment in MGM Resorts International	$ 297,643,000	347,975,000
Other non-current assets	294,860,000	247,746,000
Total	5,192,735,000	731,159,000
Contingent consideration arrangement	0	(6,918,000)
MGM
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in MGM Resorts International	1,860,158,000	0
Quoted Market Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	3,734,249,000	699,589,000
Contingent consideration arrangement	0	0
Quoted Market Prices in Active Markets for Identical Assets (Level 1) | MGM
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in MGM Resorts International	1,860,158,000
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	1,453,210,000	23,075,000
Contingent consideration arrangement	0	0
Significant Other Observable Inputs (Level 2) | MGM
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in MGM Resorts International	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	5,276,000	8,495,000
Contingent consideration arrangement	0	(6,918,000)
Significant Unobservable Inputs (Level 3) | MGM
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in MGM Resorts International	0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	1,874,091,000	699,589,000
Money market funds | Quoted Market Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	1,874,091,000	699,589,000
Money market funds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Money market funds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Treasury discount notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	1,224,966,000
Marketable debt securities:	224,979,000
Treasury discount notes | Quoted Market Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0
Marketable debt securities:	0
Treasury discount notes | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	1,224,966,000
Marketable debt securities:	224,979,000
Treasury discount notes | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0
Marketable debt securities:	0
Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	3,265,000	23,075,000
Time deposits | Quoted Market Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Time deposits | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	3,265,000	23,075,000
Time deposits | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities:		8,495,000
Other non-current assets	5,276,000
Warrant | Quoted Market Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities:		0
Other non-current assets	0
Warrant | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities:		0
Other non-current assets	0
Warrant | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities:		$ 8,495,000
Other non-current assets	$ 5,276,000

FINANCIAL INSTRUMENTS AND FAI_9

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Unobservable Inputs of Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Warrant
Warrant
Balance of beginning of period	$ 8,495	$ 0
Fair value at date of acquisition	0	17,618
Fair value adjustments	(3,219)	(9,123)
Settlements	0	0
Balance at end of period	5,276	8,495
Contingent Consideration Arrangements
Contingent Consideration Arrangements
Balance at beginning of period	(6,918)	(26,657)
Fair value at date of acquisition	(1,000)	0
Fair value adjustments	6,918	19,739
Settlements	1,000	0
Balance at end of period	$ 0	$ (6,918)

FINANCIAL INSTRUMENTS AND FA_10

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Carrying Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable - related party	$ 0	$ 55,251
Current portion of long-term debt	0	(13,750)
Long-term debt, net	(712,277)	(231,946)
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable - related party	0	55,251
Current portion of long-term debt	0	(13,750)
Long-term debt, net	(712,277)	(231,946)
Unamortized original issue discount and debt issuance costs	(7,700)	(1,800)
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable - related party	0	55,251
Current portion of long-term debt	0	(13,681)
Long-term debt, net	$ (725,700)	$ (232,581)

LONG-TERM DEBT - Summary (Detai

LONG-TERM DEBT - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Aug. 20, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Less: Current portion of long-term debt	$ 0		$ 13,750
Less: unamortized debt issuance costs	7,723
Long-term debt, net	712,277		231,946
ANGI Homeservices
Debt Instrument [Line Items]
Long-term debt	720,000		247,500
Less: Current portion of long-term debt	0		13,750
Less: unamortized debt issuance costs	7,723		1,804
Long-term debt, net	712,277		231,946
ANGI Homeservices | Senior Notes | ANGI 3.875% Senior Notes
Debt Instrument [Line Items]
Long-term debt	500,000		0
Stated interest rate (as a percent)		3.875%
ANGI Homeservices | Term Loan | ANGI Group Term Loan due November 5, 2023 ("ANGI Group Term Loan")
Debt Instrument [Line Items]
Long-term debt	$ 220,000		$ 247,500

LONG-TERM DEBT - Debt Instrumen

LONG-TERM DEBT - Debt Instrument Redemption (Details) - Senior Notes - ANGI 3.875% Senior Notes - ANGI Homeservices	Aug. 20, 2020
Period One
Debt Instrument [Line Items]
Redemption rate (as a percent)	101.938%
Period Two
Debt Instrument [Line Items]
Redemption rate (as a percent)	100.969%
Period Three
Debt Instrument [Line Items]
Redemption rate (as a percent)	100.00%

LONG-TERM DEBT - Narrative (Det

LONG-TERM DEBT - Narrative (Details)	12 Months Ended
	Dec. 31, 2023USD ($)	Dec. 31, 2022USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Aug. 20, 2020USD ($)	Nov. 05, 2018USD ($)
Debt Instrument [Line Items]
Prepaid debt principal payments				$ 13,800,000
ANGI Homeservices
Debt Instrument [Line Items]
Long-term debt, gross				720,000,000	$ 247,500,000
ANGI 3.875% Senior Notes | Senior Notes | ANGI Homeservices
Debt Instrument [Line Items]
Face amount of debt instrument						$ 500,000,000
Long-term debt, gross				$ 500,000,000	0
Debt Instrument, Covenant, Leverage Ratio, Maximum				3.75
ANGI Group Term Loan due November 5, 2023 ("ANGI Group Term Loan") | Term Loan | ANGI Homeservices
Debt Instrument [Line Items]
Long-term debt, gross				$ 220,000,000	$ 247,500,000
Basis spread on variable rate (as a percent)				2.16%	3.25%
Leverage ratio				4.5
Interest coverage ratio				2
Covenant Terms, leverage ratio limiting ability to pay dividends, make distributions, or repurchase stock				4.25
ANGI Group Term Loan due November 5, 2023 ("ANGI Group Term Loan") | Term Loan | ANGI Homeservices | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				2.00%	1.50%
ANGI Group Term Loan due November 5, 2023 ("ANGI Group Term Loan") | Term Loan | ANGI Homeservices | Forecast
Debt Instrument [Line Items]
Quarterly repayments of principal	$ 10,300,000	$ 6,900,000	$ 3,400,000
Repayments of principal, final payment	$ 161,600,000
ANGI Homeservices Credit Facility | ANGI Homeservices | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity							$ 250,000,000
Long-term line of credit				$ 0	$ 0
commitment fee (in basis points)				0.35%	0.25%

LONG-TERM DEBT - Aggregate Cont

LONG-TERM DEBT - Aggregate Contractual Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
2022	$ 27,500
2023	192,500
2028	500,000
Total	720,000
Less: unamortized debt issuance costs	7,723
Long-term debt, net	$ 712,277	$ 231,946

SHAREHOLDERS' EQUITY - Narrativ

SHAREHOLDERS' EQUITY - Narrative (Details) shares in Millions	12 Months Ended
	Dec. 31, 2020Voteshares
Class of Stock
Directors elected (as a percent)	25.00%
Stock authorized for repurchase (shares) | shares	8
Class B Common Stock
Class of Stock
Number of votes	10
Common Stock
Class of Stock
Number of votes	1

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS - Summary (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Loss
Balance at beginning of period	$ 3,005,146,000	$ 2,684,400,000	$ 2,256,320,000
Other Comprehensive Income (Loss), Net of Tax	7,812,000	308,000	(6,441,000)
Balance at end of period	7,150,928,000	3,005,146,000	2,684,400,000
Tax provision (benefit) on accumulated other comprehensive loss	0	0	0
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Loss
Balance at beginning of period	(12,226,000)	(12,543,000)	(7,504,000)
Balance at end of period	(6,172,000)	(12,226,000)	(12,543,000)
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Loss
Other comprehensive (loss) income before reclassifications	6,236,000	337,000	(4,976,000)
Amounts reclassified to earnings	(144,000)		(52,000)
Other Comprehensive Income (Loss), Net of Tax	6,092,000	337,000	(5,028,000)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Loss
Other Comprehensive Income (Loss), Net of Tax	(38,000)	(20,000)	(11,000)
Unrealized Gains On Available-For-Sale Marketable Debt Securities
Accumulated Other Comprehensive Loss
Balance at beginning of period	0	2,000	0
Balance at end of period	2,000	0	2,000
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Including Noncontrolling Interest
Accumulated Other Comprehensive Loss
Other comprehensive (loss) income before reclassifications	2,000	(2,000)	2,000
Amounts reclassified to earnings	0		0
Other Comprehensive Income (Loss), Net of Tax	2,000	(2,000)	2,000
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Noncontrolling Interest
Accumulated Other Comprehensive Loss
Other Comprehensive Income (Loss), Net of Tax	0	0	0
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Loss
Balance at beginning of period	(12,226,000)	(12,541,000)	(7,504,000)
Balance at end of period	(6,170,000)	(12,226,000)	(12,541,000)
AOCI Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Loss
Other comprehensive (loss) income before reclassifications	6,238,000	335,000	(4,974,000)
Amounts reclassified to earnings	(144,000)		(52,000)
Other Comprehensive Income (Loss), Net of Tax	6,094,000	335,000	(5,026,000)
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Loss
Other Comprehensive Income (Loss), Net of Tax	$ (38,000)	$ (20,000)	$ (11,000)

EARNINGS PER SHARE - Summary (D

EARNINGS PER SHARE - Summary (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 05, 2020	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator: Basic
Net earnings										$ 268,586	$ 32,183	$ 292,371
Net loss (earnings) attributable to noncontrolling interests										1,140	(9,288)	(45,599)
Net earnings attributable to IAC shareholders		$ 509,125	$ 184,917	$ (96,117)	$ (328,199)	$ 6,887	$ 16,466	$ 13,789	$ (14,247)	269,726	22,895	246,772
Numerator: Diluted
Net earnings										268,586	32,183	292,371
Net loss (earnings) attributable to noncontrolling interests										1,140	(9,288)	(45,599)
Impact from public subsidiaries' dilutive securities										71	0	0
Net earnings attributable to IAC shareholders										$ 269,797	$ 22,895	$ 246,772
Denominator: Basic
Weighted average basic shares outstanding (shares)										85,355,000	85,132,000	85,132,000
Denominator: Diluted
Weighted average basic shares outstanding (shares)										85,355,000	85,132,000	85,132,000
Dilutive securities (shares)										5,593,000	0	0
Denominator for earnings per share - weighted average shares (shares)										90,948,000	85,132,000	85,132,000
Earnings (loss) per share attributable to IAC shareholders: Basic
Loss (earnings) per share (USD per share)		$ 5.96	$ 2.17	$ (1.13)	$ (3.86)	$ 0.08	$ 0.19	$ 0.16	$ (0.17)	$ 3.16	$ 0.27	$ 2.90
Earnings (loss) per share attributable to IAC shareholders: Diluted
Loss (earnings) per share (USD per share)		$ 5.59	$ 2.04	$ (1.13)	$ (3.86)	$ 0.08	$ 0.19	$ 0.16	$ (0.17)	$ 2.97	$ 0.27	$ 2.90
Anti-dilutive weighted average common shares
Term of employment agreement and restricted stock agreement (in years)	10 years
Potentially dilutive securities excluded from calculation of diluted earnings per share (shares)										3,100,000
Chief Executive Officer | Restricted Stock Awards | RSA Agreement
Anti-dilutive weighted average common shares
Shares authorized for issuance (in shares)	3,000,000

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) $ / shares in Units, $ in Thousands	Jan. 29, 2021USD ($)shares	Nov. 05, 2020USD ($)$ / sharesshares	Jan. 31, 2021USD ($)$ / shares	Dec. 31, 2020USD ($)plan$ / sharesshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)
Share-based Compensation Arrangement by Share-based Payment Award
Number of active stock-based compensation plans | plan				1
Shares available for grant (shares) | shares				31,100,000
Stock options granted in period (shares) | shares				0
Unrecognized compensation cost, net of estimated forfeitures				$ 398,300
Weighted-average period over which cost is expected to be recognized (in years)				6 years 2 months 12 days
Tax benefit recognized related to stock-based compensation				$ 204,300	$ 82,400	$ 80,700
Term of employment agreement and restricted stock agreement (in years)		10 years
Intrinsic value of stock options exercised				74,800
Stock options outstanding aggregate intrinsic value				657,704
Incremental compensation cost				$ 20,500
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares required to settle vested and unvested interests at fair value (shares) | shares	3,900,000
Cash received from stock option exercises	$ 82,300
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stated term (in years)				10 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Tax benefit realized from stock option exercises				$ 170,100	$ 64,200	63,600
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award
Equity instruments other than options, outstanding (shares) | shares				0
Restricted Stock Units (RSUs) & Market Based Stock Units | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares required to settle vested and unvested interests at fair value (shares) | shares	700,000
Cash withholding obligation	$ 152,700
Withholding rate (as a percent)	50.00%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (in years)				4 years
Equity instruments other than options, outstanding (shares) | shares				1,503,000	421,000
Weighted average grant date fair value of RSUs and PSUs granted (USD per share) | $ / shares				$ 128.82
Granted (shares) | shares				1,121,000
Fair value of RSUs and PSUs that vested during the period				$ 3,800
Market-Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Equity instruments other than options, outstanding (shares) | shares				0	347,000
Weighted average grant date fair value of RSUs and PSUs granted (USD per share) | $ / shares				$ 0
Granted (shares) | shares				0
Fair value of RSUs and PSUs that vested during the period				$ 43,600
Restricted Stock Awards | RSA Agreement
Share-based Compensation Arrangement by Share-based Payment Award
Weighted average grant date fair value of RSUs and PSUs granted (USD per share) | $ / shares		$ 61.06
Equity instruments other than options, aggregate intrinsic value, outstanding		$ 183,200
Restricted Stock Awards | RSA Agreement | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for issuance (in shares) | shares		3,000,000
Vesting period (in years)		10 years
Market-Based Stock Options | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Withholding rate (as a percent)	50.00%
Stock options outstanding aggregate intrinsic value	$ 737,900
Cash withholding obligation equivalent (shares) | shares	1,800,000
Cash required to settle vested and unvested interests at fair value	$ 369,000
Stock Appreciation Rights (SARs) | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares required to settle vested and unvested interests at fair value (shares) | shares	100,000
Withholding rate (as a percent)	50.00%
Cash required to settle vested and unvested interests at fair value	$ 12,500
IAC
Share-based Compensation Arrangement by Share-based Payment Award
Transaction exchange ratio				2.1584%
Match Group
Share-based Compensation Arrangement by Share-based Payment Award
Incremental compensation cost				$ 56,900
Incremental compensation cost from modification recognized in year of modification				56,000
ANGI Homeservices
Share-based Compensation Arrangement by Share-based Payment Award
Incremental compensation cost				14,100	$ 13,100	11,800
Incremental compensation cost from modification recognized in year of modification						3,900
ANGI Homeservices | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Equity instruments other than options, aggregate intrinsic value, outstanding	$ 162,200
Withholding rate (as a percent)	50.00%
Cash withholding obligation equivalent (shares) | shares	5,800,000
Cash required to settle vested and unvested interests at fair value	$ 81,100
ANGI Homeservices | Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award
Incremental compensation cost				217,700
Incremental compensation cost from modification recognized in year of modification				21,100	$ 29,000	$ 56,900
Incremental compensation cost from modification recognized in future period				$ 900
ANGI Homeservices | Stock Appreciation Rights (SARs) | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Equity instruments other than options, aggregate intrinsic value, outstanding	$ 92,100
Withholding rate (as a percent)	50.00%
Cash withholding obligation equivalent (shares) | shares	3,300,000
Cash required to settle vested and unvested interests at fair value	$ 46,100
Vimeo | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Equity instruments other than options, aggregate intrinsic value, outstanding	$ 405,100
Withholding rate (as a percent)	50.00%
Cash required to settle vested and unvested interests at fair value	$ 202,600
Vimeo | Subsequent Event | Class B Common Stock | Sale of Equity Capital
Share-based Compensation Arrangement by Share-based Payment Award
Price per share of stock issued in sale of equity capital (in dollars per share) | $ / shares			$ 35.35
Enterprise valuation of Vimeo			$ 5,700,000
Minimum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (in years)				3 years
Minimum | Restricted Stock Awards | RSA Agreement | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (in years)		10 years
Maximum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (in years)				5 years
Maximum | Restricted Stock Awards | RSA Agreement | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (in years)		12 years

STOCK-BASED COMPENSATION - Outs

STOCK-BASED COMPENSATION - Outstanding and Unvested RSUs and MSUs (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Restricted Stock Units (RSUs)
Number of Shares
Balance at beginning of the period (shares) | shares	421,000
Granted (shares) | shares	1,121,000
Vested (shares) | shares	(26,000)
Forfeited (shares) | shares	(13,000)
Balance at end of the period (shares) | shares	1,503,000
Weighted Average Grant Date Fair Value
Balance at beginning of the period (USD per share) | $ / shares	$ 48.13
Granted (USD per share) | $ / shares	128.82
Vested (USD per share) | $ / shares	64.52
Forfeited (USD per share) | $ / shares	94.17
Balance at end of the period (USD per share) | $ / shares	$ 107.62
Market-Based Stock Units
Number of Shares
Balance at beginning of the period (shares) | shares	347,000
Granted (shares) | shares	0
Vested (shares) | shares	(347,000)
Balance at end of the period (shares) | shares	0
Weighted Average Grant Date Fair Value
Balance at beginning of the period (USD per share) | $ / shares	$ 44.76
Granted (USD per share) | $ / shares	0
Vested (USD per share) | $ / shares	44.76
Balance at end of the period (USD per share) | $ / shares	$ 0

STOCK-BASED COMPENSATION - Chan

STOCK-BASED COMPENSATION - Changes in Outstanding Stock Options (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Number of Shares
Balance at beginning of period (shares) | shares	4,498
Granted (shares) | shares	0
Exercised (shares) | shares	(587)
Forfeited (shares) | shares	0
Expired (shares) | shares	(2)
Balance at end of period (shares) | shares	3,909
Options exercisable (shares) | shares	3,909
Weighted Average Exercise Price
Balance at beginning of period (USD per share) | $ / shares	$ 20.08
Granted (USD per share) | $ / shares	0
Exercised (USD per share) | $ / shares	13.46
Forfeited (USD per share) | $ / shares	0
Expired (USD per share) | $ / shares	14.05
Balance at end of period (USD per share) | $ / shares	21.08
Options exercisable (USD per share) | $ / shares	$ 21.08
Weighted Average Remaining Contractual Term in Years
Remaining term at end of period	4 years 10 months 24 days
Term of options exercisable	4 years 10 months 24 days
Aggregate Intrinsic Value
Balance at end of period | $	$ 657,704
Options exercisable | $	$ 657,704

STOCK-BASED COMPENSATION - Stoc

STOCK-BASED COMPENSATION - Stock Options Outstanding and Exercisable (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Options Outstanding
Options outstanding (shares) | shares	3,909
Weighted- Average Remaining Contractual Life in Years	4 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 21.08
Options Exercisable
Options exercisable (shares) | shares	3,909
Weighted- Average Remaining Contractual Life in Years	4 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 21.08
Less than $20.00
Options Outstanding
Options outstanding (shares) | shares	1,060
Weighted- Average Remaining Contractual Life in Years	4 years 8 months 12 days
Weighted-average exercise price (USD per share)	$ 14.21
Options Exercisable
Options exercisable (shares) | shares	1,060
Weighted- Average Remaining Contractual Life in Years	4 years 8 months 12 days
Weighted-average exercise price (USD per share)	$ 14.21
Exercise price range, upper limit (USD per share)	$ 20
$20.01 to $30.00
Options Outstanding
Options outstanding (shares) | shares	2,765
Weighted- Average Remaining Contractual Life in Years	4 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 22.96
Options Exercisable
Options exercisable (shares) | shares	2,765
Weighted- Average Remaining Contractual Life in Years	4 years 10 months 24 days
Weighted-average exercise price (USD per share)	$ 22.96
$30.01 to $40.00
Options Outstanding
Options outstanding (shares) | shares	4
Weighted- Average Remaining Contractual Life in Years	6 years 7 months 6 days
Weighted-average exercise price (USD per share)	$ 31.82
Options Exercisable
Options exercisable (shares) | shares	4
Weighted- Average Remaining Contractual Life in Years	6 years 7 months 6 days
Weighted-average exercise price (USD per share)	$ 31.82
$40.01 to $50.00
Options Outstanding
Options outstanding (shares) | shares	80
Weighted- Average Remaining Contractual Life in Years	7 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 46.61
Options Exercisable
Options exercisable (shares) | shares	80
Weighted- Average Remaining Contractual Life in Years	7 years 2 months 12 days
Weighted-average exercise price (USD per share)	$ 46.61
Minimum | $20.01 to $30.00
Options Exercisable
Exercise price range, lower limit (USD per share)	20.01
Minimum | $30.01 to $40.00
Options Exercisable
Exercise price range, lower limit (USD per share)	30.01
Minimum | $40.01 to $50.00
Options Exercisable
Exercise price range, lower limit (USD per share)	40.01
Maximum | $20.01 to $30.00
Options Exercisable
Exercise price range, upper limit (USD per share)	30
Maximum | $30.01 to $40.00
Options Exercisable
Exercise price range, upper limit (USD per share)	40
Maximum | $40.01 to $50.00
Options Exercisable
Exercise price range, upper limit (USD per share)	$ 50

SEGMENT INFORMATION - Segment R

SEGMENT INFORMATION - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenue	$ 848,819	$ 788,377	$ 726,361	$ 684,124	$ 670,514	$ 705,382	$ 688,685	$ 641,220	$ 3,047,681	$ 2,705,801	$ 2,533,048
Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue									1,467,925	1,326,205	1,132,241
Adjusted EBITDA									172,804	202,297	247,506
Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenue									283,218	196,015	159,641
Adjusted EBITDA									(11,187)	(41,790)	(28,045)
Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenue									213,753	167,594	130,991
Adjusted EBITDA									66,206	39,601	21,384
Operating Segments | Search
Segment Reporting Information [Line Items]
Revenue									613,274	742,184	823,950
Adjusted EBITDA									51,344	124,163	182,905
Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue									469,759	274,107	286,586
Adjusted EBITDA									(37,699)	(28,368)	(14,889)
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenue									(248)	(304)	(361)
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA									$ (147,502)	$ (88,617)	$ (74,011)

SEGMENT INFORMATION - Revenue D

SEGMENT INFORMATION - Revenue Disaggregated by Service (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 848,819	$ 788,377	$ 726,361	$ 684,124	$ 670,514	$ 705,382	$ 688,685	$ 641,220	$ 3,047,681	$ 2,705,801	$ 2,533,048
Felix
Segment Reporting Information [Line Items]
Revenues											36,900
Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,467,925	1,326,205	1,132,241
Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenues									283,218	196,015	159,641
Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenues									213,753	167,594	130,991
Operating Segments | Search
Segment Reporting Information [Line Items]
Revenues									613,274	742,184	823,950
Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									469,759	274,107	286,586
North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,395,428	1,249,892	1,062,171
Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									72,497	76,313	70,070
Marketplace | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									138,726	38,950	19,665
Marketplace | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,131,320	992,668	774,495
Consumer Connection | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,054,660	913,533	704,341
Membership Subscription | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									50,975	63,872	66,214
Other | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									25,685	15,263	3,940
Advertising and Other | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									264,108	257,224	287,676
Advertising and Other | Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,714	2,471	1,795
Consumer Connection | Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									57,692	59,611	50,913
Membership Subscription | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									303,482	194,362	102,592
Membership Subscription | Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									13,091	14,231	17,362
Platform | Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenues									283,218	193,736	146,665
Hardware | Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenues									0	2,279	12,976
Advertising | Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenues									137,455	126,350	103,704
Advertising | Operating Segments | Search
Segment Reporting Information [Line Items]
Revenues									596,363	726,021	802,469
Advertising | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									19,366	27,858	78,712
Google Advertising | Operating Segments | Search
Segment Reporting Information [Line Items]
Revenues									506,077	678,438	770,494
Google Advertising | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									3,130	4,486	14,393
Other | Operating Segments | Search
Segment Reporting Information [Line Items]
Revenues									90,286	47,583	31,975
Other | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									16,236	23,372	64,319
Affiliate Commerce Commission | Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenues									76,298	41,244	27,287
Media Production and Distribution | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									3,585	8,897	61,717
Other | Operating Segments | Search
Segment Reporting Information [Line Items]
Revenues									16,911	16,163	21,481
Other | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									190	159	1,758
Service | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									$ 4,410	$ 3,881	$ 22,142

SEGMENT INFORMATION - Revenue a

SEGMENT INFORMATION - Revenue and Long-Lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue and Long-lived Assets by Geography
Revenue:	$ 3,047,681	$ 2,705,801	$ 2,533,048
Long-lived assets (excluding goodwill and intangible assets)	278,251	305,414
United States
Revenue and Long-lived Assets by Geography
Revenue:	2,449,257	2,097,743	1,951,957
Long-lived assets (excluding goodwill and intangible assets)	266,169	297,433
All other countries
Revenue and Long-lived Assets by Geography
Revenue:	598,424	608,058	$ 581,091
Long-lived assets (excluding goodwill and intangible assets)	$ 12,082	$ 7,981

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation of Adjusted EBITDA to Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Other Significant Reconciling Item
Operating loss	$ (24,366)	$ (128,626)	$ (107,019)	$ (312,338)	$ (16,408)	$ 13,912	$ (13,770)	$ (34,183)	$ (572,349)	$ (50,449)	$ 35,835
Stock-Based Compensation Expense									197,220	134,338	148,405
Depreciation									69,283	55,949	42,393
Amortization of intangibles									141,584	83,868	107,081
Goodwill Impairment									265,146	3,318	0
Interest expense									(16,166)	(11,904)	(13,059)
Unrealized gain on investment in MGM Resorts International									840,550	0	0
Other expense, net									(42,468)	34,047	282,795
Earnings (loss) before income taxes									209,567	(28,306)	305,571
Taxes									59,019	60,489	(13,200)
Net earnings	507,360	185,861	(94,064)	(330,571)	5,457	18,378	22,021	(13,673)	268,586	32,183	292,371
Net loss (earnings) attributable to noncontrolling interests									1,140	(9,288)	(45,599)
Net earnings attributable to IAC shareholders	$ 509,125	$ 184,917	$ (96,117)	$ (328,199)	$ 6,887	$ 16,466	$ 13,789	$ (14,247)	269,726	22,895	246,772
ANGI Homeservices
Segment Reporting, Other Significant Reconciling Item
Goodwill Impairment									0	0
Search
Segment Reporting, Other Significant Reconciling Item
Goodwill Impairment									265,146	0
Emerging & Other
Segment Reporting, Other Significant Reconciling Item
Goodwill Impairment									0	3,318
Operating Segments | ANGI Homeservices
Segment Reporting, Other Significant Reconciling Item
Operating loss									(6,368)	38,645	63,906
Stock-Based Compensation Expense									83,649	68,255	97,078
Depreciation									52,621	39,915	24,310
Amortization of intangibles									42,902	55,482	62,212
Acquisition-related Contingent Consideration Fair Value Adjustments									0	0	0
Goodwill Impairment									0	0
Adjusted EBITDA									172,804	202,297	247,506
Operating Segments | Vimeo
Segment Reporting, Other Significant Reconciling Item
Operating loss									(26,392)	(51,921)	(35,594)
Stock-Based Compensation Expense									0	0	0
Depreciation									460	478	1,200
Amortization of intangibles									14,745	9,653	6,349
Acquisition-related Contingent Consideration Fair Value Adjustments									0	0	0
Goodwill Impairment									0	0
Adjusted EBITDA									(11,187)	(41,790)	(28,045)
Operating Segments | Dotdash
Segment Reporting, Other Significant Reconciling Item
Operating loss									50,241	29,021	18,778
Stock-Based Compensation Expense									0	0	0
Depreciation									1,794	974	969
Amortization of intangibles									14,171	9,606	1,637
Acquisition-related Contingent Consideration Fair Value Adjustments									0	0	0
Goodwill Impairment									0	0
Adjusted EBITDA									66,206	39,601	21,384
Operating Segments | Search
Segment Reporting, Other Significant Reconciling Item
Operating loss									(248,711)	122,347	151,425
Stock-Based Compensation Expense									0	0	0
Depreciation									2,709	1,816	3,311
Amortization of intangibles									32,200	0	28,169
Acquisition-related Contingent Consideration Fair Value Adjustments									0	0	0
Goodwill Impairment									265,146	0
Adjusted EBITDA									51,344	124,163	182,905
Operating Segments | Emerging & Other
Segment Reporting, Other Significant Reconciling Item
Operating loss									(70,896)	(21,790)	(26,627)
Stock-Based Compensation Expense									100	0	919
Depreciation									2,449	715	969
Amortization of intangibles									37,566	9,127	8,714
Acquisition-related Contingent Consideration Fair Value Adjustments									(6,918)	(19,738)	1,136
Goodwill Impairment									0	3,318
Adjusted EBITDA									(37,699)	(28,368)	(14,889)
Corporate
Segment Reporting, Other Significant Reconciling Item
Operating loss									(270,223)	(166,751)	(136,053)
Stock-Based Compensation Expense									113,471	66,083	50,408
Depreciation									9,250	12,051	11,634
Amortization of intangibles									0	0	0
Acquisition-related Contingent Consideration Fair Value Adjustments									0	0	0
Goodwill Impairment									0	0
Adjusted EBITDA									$ (147,502)	$ (88,617)	$ (74,011)

SEGMENT INFORMATION - Capital E

SEGMENT INFORMATION - Capital Expenditures by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Capital expenditures:	$ 61,570	$ 97,898	$ 54,680
Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Capital expenditures:	52,488	68,804	46,976
Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Capital expenditures:	844	2,801	209
Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Capital expenditures:	5,445		102
Operating Segments | Search
Segment Reporting Information [Line Items]
Capital expenditures:	47	43	479
Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Capital expenditures:	1,363	387	751
Corporate
Segment Reporting Information [Line Items]
Capital expenditures:	$ 1,383	$ 25,863	$ 6,163

LEASES - Balance Sheet Informat

LEASES - Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Other non-current assets	$ 171,741	$ 138,608
Liabilities:
Current lease liabilities	27,785	23,188
Long-term lease liabilities	206,389	168,321
Total lease liabilities	$ 234,174	$ 191,509
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent

LEASES - Lease Cost (Details)

LEASES - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 39,882	$ 30,413
Variable lease cost	10,705	7,776
Lease cost	50,587	38,189
Vacating office space cost	5,800	4,900
Short-term lease cost	2,800	2,200
Sublease income	5,300	7,600
Cost of revenue
Lessee, Lease, Description [Line Items]
Operating lease cost	2,214	547
Variable lease cost	0	83
Selling and marketing expense
Lessee, Lease, Description [Line Items]
Operating lease cost	12,779	10,613
Variable lease cost	2,314	1,573
General and administrative expense
Lessee, Lease, Description [Line Items]
Operating lease cost	21,433	17,751
Variable lease cost	7,452	5,729
Product development expense
Lessee, Lease, Description [Line Items]
Operating lease cost	3,456	1,502
Variable lease cost	$ 939	$ 391

LEASES - Operating Lease Liabil

LEASES - Operating Lease Liabilities Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2021	$ 38,664
2022	38,473
2023	36,648
2024	35,106
2025	26,841
Thereafter	227,409
Total	403,141
Less: Interest	168,967
Present value of lease liabilities	234,174	$ 191,509
Lease payments for leases signed but not yet commenced	$ 100

LEASES - Weighted-Average Remai

LEASES - Weighted-Average Remaining Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Remaining lease term (in years)	15 years 4 months 24 days	17 years 4 months 24 days
Discount rate (as a percent)	5.66%	6.12%

LEASES - Other Information (Det

LEASES - Other Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Right-of-use assets obtained in exchange for lease liabilities	$ 81,636	$ 61,657
Cash paid for amounts included in the measurement of lease liabilities	$ 44,978	$ 35,321

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Commercial Commitments Outstanding (Details) - Purchase obligations $ in Thousands	Dec. 31, 2020USD ($)
Other Commitments
Less Than 1 Year	$ 45,819
1-3 Years	520
3-5 Years	0
More Than 5 Years	0
Total Amounts Committed	$ 46,339

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Narrative (Details)	1 Months Ended			12 Months Ended
	Jul. 31, 2020plaintiff	Aug. 31, 2018plaintiff	Aug. 31, 2018USD ($)plaintiff	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2017item	Jun. 30, 2020USD ($)
Loss Contingencies [Line Items]
Loss contingency accrual				$ 0
Tinder Optionholder Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff	6	6	10
Number of investment banks involved | item						2
Number of plaintiffs who filed a discontinuance of claims | plaintiff			4
Number of plaintiffs who filed a notice of discontinuance of their claims without prejudice | plaintiff	4
Tinder Optionholder Litigation | Pending Litigation
Loss Contingencies [Line Items]
Damages sought			$ 2,000,000,000
Purchase Commitment - Three Year Cloud Computing
Loss Contingencies [Line Items]
Purchase obligations				$ 150,000,000
Term of commercial commitment (in years)				3 years
Payments of commercial commitments					$ 50,000,000
Prepaid asset				$ 9,800,000
Commercial commitments due in the next twelve months				10,000,000
Purchase Commitment - Three Year Cloud Computing | IAC
Loss Contingencies [Line Items]
Purchase obligations							$ 20,000,000
Payments of commercial commitments				$ 10,000,000
Purchase Commitment - Three Year Cloud Computing | Match Group
Loss Contingencies [Line Items]
Purchase obligations							$ 80,000,000
Purchase Commitment - Two Year Cloud Computing
Loss Contingencies [Line Items]
Term of commercial commitment (in years)				2 years
Commercial commitments due in the next twelve months				$ 14,400,000
Purchase obligations
Loss Contingencies [Line Items]
Purchase obligations				46,339,000
Commercial commitments due in the next twelve months				45,819,000
Commercial commitments due between Year One and Year Three				520,000
Purchase Commitments - Advertising
Loss Contingencies [Line Items]
Commercial commitments due in the next twelve months				$ 6,900,000
Expedia | Corporate Aircraft Purchase
Loss Contingencies [Line Items]
Proportion of total purchase price and refurbish costs paid in related party transaction (as a percent)				50.00%
Expedia | Corporate Aircraft Purchase | Purchase obligations
Loss Contingencies [Line Items]
Commercial commitments due in the next twelve months				$ 13,200,000

RELATED PARTY TRANSACTIONS - Na

RELATED PARTY TRANSACTIONS - Narrative (Details) shares in Millions	Jan. 31, 2020building	Oct. 10, 2018shares	Mar. 31, 2019USD ($)	Jun. 30, 2020USD ($)shares	Dec. 31, 2020USD ($)aircraftshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)shares	Dec. 14, 2018USD ($)
Related Party Transaction [Line Items]
Notes receivable from related parties				$ 27,200,000		$ 55,300,000
Angie's List Merger Agreement | Class B Common Stock
Related Party Transaction [Line Items]
Stock issued during period to related party (shares) | shares		5.1
Affiliated Entity
Related Party Transaction [Line Items]
Allocated costs from related party					$ 85,500,000	146,000,000	$ 178,200,000
Interest income from related party (less than)					$ 100,000	400,000	300,000
Due to related parties							2,500,000	$ 15,000,000
Allocation of costs from Old IAC				12,652,000		$ 80,143,000	$ 71,977,000
Subsidiary of Common Parent | Employee Matters Agreement | Class B Common Stock | ANGI Homeservices
Related Party Transaction [Line Items]
Stock received from related party (shares) | shares					0.3	0.5	0.9
Subsidiary of Common Parent | Service Agreements
Related Party Transaction [Line Items]
Due from (to) related party					$ 0
Subsidiary of Common Parent | Leased Office Space
Related Party Transaction [Line Items]
Allocation of costs from Old IAC				1,400,000		$ 5,800,000	$ 5,200,000
Subsidiary of Common Parent | Sold Office Space
Related Party Transaction [Line Items]
Allocation of costs from Old IAC				$ 100,000
Number of office buildings transferred to related party | building	2
Subsidiary of Common Parent | Sold Office Space | Common Stock
Related Party Transaction [Line Items]
Noncash financial or equity instrument consideration (in shares) | shares				1.4
Limited Liability Company | Service Agreements | ANGI Homeservices
Related Party Transaction [Line Items]
Allocation of costs from Old IAC					4,800,000	4,800,000	5,700,000
Limited Liability Company | Tax Sharing Agreement | ANGI Homeservices
Related Party Transaction [Line Items]
Due to related parties					900,000	200,000
Allocation of costs from Old IAC			$ 11,400,000
Refunds paid to related party					3,100,000
Limited Liability Company | Leased Office Space | ANGI Homeservices
Related Party Transaction [Line Items]
Due to related parties					100,000	100,000
Allocation of costs from Old IAC					$ 1,800,000	1,400,000	$ 0
Other Affiliates | Corporate Aircraft Purchase
Related Party Transaction [Line Items]
Allocation of costs from Old IAC						23,000,000
Proportion of ownership interest held each by entity and by related party in aircraft employing flight crew (as a percent)					50.00%
Number of aircraft operated | aircraft					2
Expected costs from transactions with related party						$ 72,300,000
Proportion of total purchase price and refurbish costs paid in related party transaction (as a percent)						50.00%
Proportion of ownership interest held each by entity and by related party in another entity employing flight crew (as a percent)					50.00%

RELATED PARTY TRANSACTIONS - Co

RELATED PARTY TRANSACTIONS - Components of Net Increase (decrease) in IAC Investment n IAC Holdings (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Taxes		$ 59,019	$ 60,489	$ (13,200)
Affiliated Entity
Related Party Transaction [Line Items]
Cash transfers (from) to Old IAC related to its centrally managed U.S. treasury management function, acquisitions and cash expenses paid by Old IAC on behalf of the Company, net	$ (1,742,854)		(182,382)	215,993
Contribution of buildings to Match Group	34,973		0	0
Taxes	34,436		(1,874)	1,120
Allocation of costs from Old IAC	12,652		80,143	71,977
Interest income, net	102		420	325
Net (increase) decrease in Old IAC's investment in the Company prior to the MTCH Separation	$ (1,685,995)		$ (263,979)	$ 145,461

BENEFIT PLANS - Narrative (Deta

BENEFIT PLANS - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended			18 Months Ended
	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Defined Contribution Plan Disclosure
Employee contribution limit per calendar year (up to) (as a percent of pre-tax earnings)		50.00%
Employer contribution limit per calendar year (as a percent of compensation)	6.00%				10.00%
Employer contribution per dollar employee contributes up to contribution limit	50.00%				100.00%
United States
Defined Contribution Plan Disclosure
Defined contribution plan contributions		$ 20.5	$ 15.4	$ 10.2
Foreign Plan
Defined Contribution Plan Disclosure
Defined contribution plan contributions		$ 1	$ 1	$ 0.6

FINANCIAL STATEMENT DETAILS - C

FINANCIAL STATEMENT DETAILS - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 3,476,188	$ 839,796	$ 884,975	$ 757,202
Restricted cash included in other current assets	473	527	1,441	2,737
Restricted cash included in other assets	449	409	420	0
Total cash and cash equivalents and restricted cash as shown on the statement of cash flows	$ 3,477,110	$ 840,732	$ 886,836	$ 759,939

FINANCIAL STATEMENT DETAILS - O

FINANCIAL STATEMENT DETAILS - Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2018
Other current assets:
Prepaid expenses	$ 50,123	$ 41,934
Capitalized costs to obtain a contract with a customer	61,514	43,069	$ 40,600
Capitalized downloadable search toolbar costs, net	12,730	21,985
Other	23,263	45,346
Other current assets	$ 147,630	$ 152,334

FINANCIAL STATEMENT DETAILS - P

FINANCIAL STATEMENT DETAILS - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Building, capitalized software, leasehold improvements and equipment	$ 486,363	$ 507,212
Accumulated depreciation and amortization	(208,112)	(201,798)
Building, capitalized software, leasehold improvements and equipment, net	278,251	305,414
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Building, capitalized software, leasehold improvements and equipment	198,778	242,882
Capitalized software and computer equipment
Property, Plant and Equipment [Line Items]
Building, capitalized software, leasehold improvements and equipment	149,789	124,523
Furniture and other equipment
Property, Plant and Equipment [Line Items]
Building, capitalized software, leasehold improvements and equipment	84,161	84,640
Land
Property, Plant and Equipment [Line Items]
Building, capitalized software, leasehold improvements and equipment		11,591
Projects in progress
Property, Plant and Equipment [Line Items]
Building, capitalized software, leasehold improvements and equipment	$ 53,635	$ 43,576

FINANCIAL STATEMENT DETAILS - A

FINANCIAL STATEMENT DETAILS - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued expenses and other current liabilities:
Accrued employee compensation and benefits	$ 126,161	$ 105,960
Accrued advertising expense	62,854	59,269
Accrued revenue share	38,710	30,574
Other	155,837	124,670
Accrued expenses and other current liabilities	$ 383,562	$ 320,473

FINANCIAL STATEMENT DETAILS -_2

FINANCIAL STATEMENT DETAILS - Other Income (Expense), Net (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other income (expense), net:
Impairments related to COVID-19		$ (59,001)	$ 0	$ 0
Realized gains related to the sale of investments		10,661	2,327	589
Realized gains related to the sale of the investment in Pinterest		0	20,486	26,777
Upward adjustments to the carrying value of equity securities without readily determinable fair values		0	18,505	128,901
Interest income		7,189	15,164	9,125
Realized gains (losses) related to the sale of business		1,061	(8,239)	121,230
Unrealized reduction in the estimated fair value of a warrant		(1,213)	(9,123)	0
Mark-to-market loss on an indemnification claim related to the Handy acquisition		(181)	(1,779)	0
Other		(984)	(3,294)	(3,827)
Other (expense) income, net		(42,468)	34,047	282,795
Condensed Income Statements, Captions [Line Items]
Impairment of equity securities without readily determinable fair value	$ 51,500	51,500
Impairment of note receivable and warrant	$ 7,500	7,500
Unrealized gain (loss) on investment		$ 840,550	$ 0	0
Pinterest
Condensed Income Statements, Captions [Line Items]
Unrealized gain (loss) on investment				$ 128,800

FINANCIAL STATEMENT DETAILS - S

FINANCIAL STATEMENT DETAILS - Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash paid (received) during the year for:
Interest	$ 6,524	$ 10,042	$ 13,108
Income tax payments	6,876	4,861	4,084
Income tax refunds	$ (2,080)	$ (3,048)	$ (30,320)

FINANCIAL STATEMENT DETAILS -_3

FINANCIAL STATEMENT DETAILS - Supplemental Disclosure of Non-Cash Transactions (Details) - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 19, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Fair value of contingent consideration at date of acquisition	$ 0	$ 0	$ 25,500,000
Common Stock
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock issued (shares)	82,976
Common stock	$ 83,000	$ 0
Common Stock | ANGI Homeservices
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock issued (shares)				8,600
Common stock				$ 165,800,000

QUARTERLY RESULTS (UNAUDITED) -

QUARTERLY RESULTS (UNAUDITED) - Summary (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Revenue	$ 848,819	$ 788,377	$ 726,361	$ 684,124	$ 670,514	$ 705,382	$ 688,685	$ 641,220	$ 3,047,681	$ 2,705,801	$ 2,533,048
Cost of revenue	249,122	207,643	178,639	179,327	152,506	158,161	149,725	139,848	814,731	600,240	501,152
Operating loss	(24,366)	(128,626)	(107,019)	(312,338)	(16,408)	13,912	(13,770)	(34,183)	(572,349)	(50,449)	35,835
Net (loss) earnings	507,360	185,861	(94,064)	(330,571)	5,457	18,378	22,021	(13,673)	268,586	32,183	292,371
Net (loss) earnings attributable to IAC shareholders	$ 509,125	$ 184,917	$ (96,117)	$ (328,199)	$ 6,887	$ 16,466	$ 13,789	$ (14,247)	$ 269,726	$ 22,895	$ 246,772
Per share information attributable to IAC shareholders:
Basic earnings per share (USD per share)	$ 5.96	$ 2.17	$ (1.13)	$ (3.86)	$ 0.08	$ 0.19	$ 0.16	$ (0.17)	$ 3.16	$ 0.27	$ 2.90
Diluted earnings per share (USD per share)	$ 5.59	$ 2.04	$ (1.13)	$ (3.86)	$ 0.08	$ 0.19	$ 0.16	$ (0.17)	$ 2.97	$ 0.27	$ 2.90
Stock-based compensation expense									$ 197,220	$ 134,338	$ 148,405
Impairment of equity securities without readily determinable fair value	$ 51,500			$ 51,500					51,500
Impairment of note receivable and warrant				7,500					7,500
Unrealized gain on investment in MGM Resorts International									840,550	$ 0	$ 0
MGM
Per share information attributable to IAC shareholders:
Unrealized gain on investment in MGM Resorts International	439,600	$ 227,700	$ (24,700)						$ 840,500
Search | Desktop
Per share information attributable to IAC shareholders:
Goodwill impairment loss, net of tax		53,200		208,900
Impairment of intangible assets		8,300		16,400
HomeAdvisor
Per share information attributable to IAC shareholders:
Stock-based compensation expense		4,100	$ 2,700	$ 8,900	$ 5,700	$ 5,700	$ 6,300	$ 7,400
Match Group
Per share information attributable to IAC shareholders:
Stock-based compensation expense	$ 1,500	$ 40,700

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, shares in Millions	Feb. 12, 2021	Jan. 31, 2021	Feb. 01, 2021	Dec. 31, 2020
Vimeo
Subsequent Event [Line Items]
Ownership interest (as a percent)				93.20%
Vimeo | Common Stock
Subsequent Event [Line Items]
Ownership interest (as a percent)				89.70%
Vimeo | Class B Common Stock
Subsequent Event [Line Items]
Ownership interest (as a percent)				97.60%
Subsequent Event | Vimeo | Sale of Equity Capital
Subsequent Event [Line Items]
Proceeds raised from sale of equity capital		$ 300,000,000
Subsequent Event | Common Stock | Vimeo | Sale of Equity Capital
Subsequent Event [Line Items]
Proceeds raised from sale of equity capital		$ 200,000,000
Number of shares issued in sale of equity capital (in shares)		6.2
Price per share of stock issued in sale of equity capital (in dollars per share)		$ 32.41
Enterprise valuation of Vimeo		$ 5,200,000,000
Subsequent Event | Class B Common Stock | Vimeo | Sale of Equity Capital
Subsequent Event [Line Items]
Proceeds raised from sale of equity capital		$ 100,000,000
Number of shares issued in sale of equity capital (in shares)		2.8
Price per share of stock issued in sale of equity capital (in dollars per share)		$ 35.35
Enterprise valuation of Vimeo		$ 5,700,000,000
Subsequent Event | Vimeo
Subsequent Event [Line Items]
Ownership interest (as a percent)			88.00%
Subsequent Event | Revolving Credit Facility | Vimeo Credit Facility
Subsequent Event [Line Items]
Term of debt instrument (years)	5 years
Maximum borrowing capacity	$ 100,000,000

SCHEDULE II - VALUATION AND Q_2

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for credit losses
Movement in Valuation Allowances and Reserves
Balance at beginning of period	$ 20,257	$ 16,344	$ 9,075
Charges to Earnings	80,765	65,723	48,362
Charges to Other Accounts	(52)	247	(451)
Deductions	(73,316)	(62,057)	(40,642)
Balance at end of period	27,654	20,257	16,344
Deferred tax valuation allowance
Movement in Valuation Allowances and Reserves
Balance at beginning of period	92,990	86,778	91,040
Charges to Earnings	11,623	7,813	(2,056)
Charges to Other Accounts	9,071	(1,601)	(2,206)
Deductions	0	0	0
Balance at end of period	113,684	92,990	86,778
Revenue reserves
Movement in Valuation Allowances and Reserves
Balance at beginning of period	3,891	1,792	1,635
Charges to Earnings	110,796	114,005	87,803
Charges to Other Accounts	0	(2)	(5)
Deductions	(112,625)	(111,904)	(87,641)
Balance at end of period	2,062	3,891	1,792
Other reserves
Movement in Valuation Allowances and Reserves
Balance at beginning of period	5,060	4,726	0
Balance at end of period	$ 8,054	$ 5,060	$ 4,726

Uncategorized Items - iaci-2021

Label	Element	Value
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update201409 [Member]