Groupon (GRPN) 10-Q 30 Apr 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	Groupon, Inc.
Entity Central Index Key	0001490281
Entity Filer Category	Large Accelerated Filer
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Common Stock, Shares Outstanding		568,198,215
Smaller Reporting Company	false
Emerging Growth Company	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 645,610	$ 841,021
Accounts receivable, net	83,658	69,493
Prepaid expenses and other current assets	82,686	88,115
Total current assets	811,954	998,629
Property, equipment and software, net	136,570	143,117
Operating Lease, Right-of-Use Asset, Net	103,101	0
Goodwill	324,579	325,491
Intangible assets, net	42,659	45,401
Investments (including $42,888 and $84,242 at March 31, 2019 and December 31, 2018, at fair value)	66,913	108,515
Other non-current assets	20,236	20,989
Total Assets	1,506,012	1,642,142
Current liabilities:
Accounts payable	25,312	38,359
Accrued merchant and supplier payables	512,728	651,781
Accrued expenses and other current liabilities	256,060	267,034
Total current liabilities	794,100	957,174
Convertible senior notes, net	204,844	201,669
Operating Lease, Liability, Noncurrent	110,999	0
Other non-current liabilities	53,673	100,688
Total Liabilities	1,163,616	1,259,531
Stockholders' Equity
Common stock, par value $0.0001 per share, 2,010,000,000 shares authorized; 764,245,924 shares issued and 567,982,801 shares outstanding at March 31, 2019; 760,939,440 shares issued and 569,084,312 shares outstanding at December 31, 2018	76	76
Additional paid-in capital	2,248,616	2,234,560
Treasury stock, at cost, 196,263,123 and 191,855,128 shares at March 31, 2019 and December 31, 2018	(892,546)	(877,491)
Accumulated deficit	(1,052,986)	(1,010,499)
Accumulated other comprehensive income (loss)	37,915	34,602
Total Groupon, Inc. Stockholders' Equity	341,075	381,248
Noncontrolling interests	1,321	1,363
Total Equity	342,396	382,611
Total Liabilities and Equity	$ 1,506,012	$ 1,642,142

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Investments at fair value	$ 42,888	$ 84,242
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	2,010,000,000	2,010,000,000
Common stock, shares issued (in shares)	764,245,924	760,939,440
Common stock, shares outstanding (in shares)	567,982,801	569,084,312
Treasury Stock
Treasury stock (in shares)	196,263,123	191,855,128

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Total revenue	$ 578,410	$ 626,540
Cost of revenue:
Total cost of revenue	272,394	301,655
Gross profit	306,016	324,885
Operating expenses:
Marketing	93,397	99,156
Selling, general and administrative	210,424	222,344
Total operating expenses	303,821	321,500
Income (loss) from operations	2,195	3,385
Other income (expense), net	(46,855)	(8,515)
Income (loss) from continuing operations before provision (benefit) for income taxes	(44,660)	(5,130)
Provision (benefit) for income taxes	(3,490)	(2,335)
Income (loss) from continuing operations	(41,170)	(2,795)
Income (loss) from discontinued operations, net of tax	2,162	0
Net income (loss)	(39,008)	(2,795)
Net income attributable to noncontrolling interests	(3,479)	(4,093)
Net income (loss) attributable to Groupon, Inc.	$ (42,487)	$ (6,888)
Basic and diluted net income (loss) per share:
Continuing operations (in usd per share)	$ (0.08)	$ (0.01)
Discontinued operations (in usd per share)	0.01	0
Basic and diluted net income (loss) per share (in usd per share)	$ (0.07)	$ (0.01)
Weighted average number of shares outstanding
Basic (in shares)	570,095,128	561,735,937
Diluted (in shares)	570,095,128	561,735,937
Comprehensive income (loss):
Net change in unrealized gain (loss) on foreign currency translation adjustments	$ 3,272	$ (1,568)
Net change in unrealized gain (loss) on available-for-sale securities (net of tax effect of $13 and $0 for the three months ended March 31, 2019 and 2018)	41	(501)
Other comprehensive income (loss)	3,313	(2,069)
Comprehensive income (loss)	(35,695)	(4,864)
Comprehensive income (loss) attributable to noncontrolling interest	3,479	(4,093)
Comprehensive income (loss) attributable to Groupon, Inc.	(39,174)	(8,957)
Service
Revenue:
Total revenue	285,827	301,797
Cost of revenue:
Total cost of revenue	28,627	31,145
Product
Revenue:
Total revenue	292,583	324,743
Cost of revenue:
Total cost of revenue	243,767	270,510
Continuing Operations [Member]
Comprehensive income (loss):
Other comprehensive income (loss)	3,313	(2,069)
Discontinued Operations, Disposed of by Sale [Member]
Comprehensive income (loss):
Other comprehensive income (loss)	$ 0	$ 0

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net change in unrealized gain (loss) on available-for-sale securities, tax	$ 13	$ 0

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total Groupon, Inc. Stockholders' Equity	Non-controlling Interests
Beginning balance (in shares) at Dec. 31, 2017		748,541,862
Beginning balance at Dec. 31, 2017	$ 251,845	$ 75	$ 2,174,708		$ (1,088,204)	$ 31,844	$ 250,973	$ 872
Treasury stock, beginning balance (in shares) at Dec. 31, 2017				(188,602,242)
Treasury stock, beginning balance at Dec. 31, 2017				$ (867,450)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle, net of tax	88,945				88,945		88,945
Reclassification for impact of U.S. tax rate change					(161)	161
Net income (loss) attributable to noncontrolling interest	(2,795)				(6,888)			4,093
Net income (loss) attributable to parent	(6,888)						(6,888)
Foreign currency translation	(1,568)					(1,568)	(1,568)
Unrealized gain (loss) on available-for-sale securities, net of tax	(501)					(501)	(501)
Exercise in stock options (in shares)		2,400
Exercise of stock options	6		6				6
Vesting of restricted stock units and performance share units (in shares)		4,157,462
Vesting of restricted stock units and performance share units			0
Shares issued under employee stock purchase plan (in shares)		746,773
Shares issued under employee stock purchase plan	2,434		2,434				2,434
Shares issued to settle liability-classified awards (in shares)		1,240,379
Shares issued to settle liability-classified awards	6,436		6,436				6,436
Tax withholdings related to net share settlements of stock-based compensation awards (in shares)		(2,024,590)
Tax withholdings related to net share settlements of stock-based compensation awards	(9,355)		(9,355)				(9,355)
Stock-based compensation on equity-classified awards	18,240		18,240				18,240
Distributions to noncontrolling interest holders	(3,315)							(3,315)
Ending balance (in shares) at Mar. 31, 2018		752,664,286
Ending balance at Mar. 31, 2018	350,372	$ 75	2,192,469		(1,006,308)	29,936	348,722	1,650
Treasury stock, ending balance (in shares) at Mar. 31, 2018				(188,602,242)
Treasury stock, ending balance at Mar. 31, 2018				$ (867,450)
Beginning balance (in shares) at Dec. 31, 2018		760,939,440
Beginning balance at Dec. 31, 2018	382,611	$ 76	2,234,560		(1,010,499)	34,602	381,248	1,363
Treasury stock, beginning balance (in shares) at Dec. 31, 2018				(191,855,128)
Treasury stock, beginning balance at Dec. 31, 2018	877,491			$ (877,491)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to noncontrolling interest	(39,008)				(42,487)			3,479
Net income (loss) attributable to parent	(42,487)						(42,487)
Foreign currency translation	3,272					3,272	3,272
Unrealized gain (loss) on available-for-sale securities, net of tax	$ 41					41	41
Exercise in stock options (in shares)	12,500	12,500
Exercise of stock options	$ 8		8				8
Vesting of restricted stock units and performance share units (in shares)	0	4,160,415
Shares issued under employee stock purchase plan (in shares)		719,297
Shares issued under employee stock purchase plan	$ 1,998		1,998				1,998
Tax withholdings related to net share settlements of stock-based compensation awards (in shares)		(1,585,728)
Tax withholdings related to net share settlements of stock-based compensation awards	(5,681)		(5,681)				(5,681)
Treasury Stock, Shares, Acquired				(4,407,995)
Treasury Stock, Value, Acquired, Par Value Method	(15,055)			$ (15,055)			(15,055)
Stock-based compensation on equity-classified awards	17,731		17,731				17,731
Distributions to noncontrolling interest holders	(3,521)							(3,521)
Ending balance (in shares) at Mar. 31, 2019		764,245,924
Ending balance at Mar. 31, 2019	342,396	$ 76	$ 2,248,616		$ (1,052,986)	$ 37,915	$ 341,075	$ 1,321
Treasury stock, ending balance (in shares) at Mar. 31, 2019				(196,263,123)
Treasury stock, ending balance at Mar. 31, 2019	$ 892,546			$ (892,546)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net income (loss)		$ (39,008)	$ (2,795)
Less: Income (loss) from discontinued operations, net of tax		2,162	0
Income (loss) from continuing operations		(41,170)	(2,795)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization of property, equipment and software		24,522	26,721
Amortization of acquired intangible assets		3,894	2,940
Stock-based compensation		16,411	19,326
Deferred income taxes		0	(6,575)
(Gain) loss from changes in fair value of investments		41,408	5,033
Amortization of debt discount on convertible senior notes		3,175	2,866
Change in assets and liabilities, net of acquisitions and dispositions:
Accounts receivable		(14,200)	17,623
Prepaid expenses and other current assets		3,461	9,601
Accounts payable		(12,914)	(8,341)
Accrued merchant and supplier payables		(136,572)	(143,330)
Accrued expenses and other current liabilities		(40,405)	(41,564)
Other, net		4,907	(1,252)
Net cash provided by (used in) operating activities from continuing operations		(147,483)	(119,747)
Net cash provided by (used in) operating activities from discontinued operations		0	0
Net cash provided by (used in) operating activities		(147,483)	(119,747)
Investing activities
Purchases of property and equipment and capitalized software		(17,477)	(20,144)
Acquisitions of intangible assets and other investing activities		(638)	(238)
Net cash provided by (used in) investing activities from continuing operations		(18,115)	(20,382)
Net cash provided by (used in) investing activities from discontinued operations		0	0
Net cash provided by (used in) investing activities		(18,115)	(20,382)
Financing activities
Payments for purchases of treasury stock		(14,416)	0
Taxes paid related to net share settlements of stock-based compensation awards		(5,090)	(9,179)
Proceeds from stock option exercises and employee stock purchase plan		2,006	2,434
Distributions to noncontrolling interest holders		(3,521)	(3,315)
Payments of finance lease obligations		(6,756)
Payments of finance lease obligations			(9,024)
Payments of contingent consideration related to acquisitions		0	(1,815)
Net cash provided by (used in) financing activities		(27,777)	(20,899)
Effect of exchange rate changes on cash, cash equivalents and restricted cash, including cash classified within current assets		(3,381)	6,191
Net increase (decrease) in cash, cash equivalents and restricted cash, including cash classified within current assets		(196,756)	(154,837)
Less: Net increase (decrease) in cash classified within current assets of discontinued operations		0	0
Net increase (decrease) in cash, cash equivalents and restricted cash		(196,756)	(154,837)
Cash, cash equivalents and restricted cash, beginning of period		844,728	885,481
Cash, cash equivalents and restricted cash, end of period (1)	[1]	647,972	730,644
Non-cash investing and financing activities
Equipment acquired under finance lease obligations		0	1,470
Liability for purchases of treasury stock		(1,095)	0
Increase (decrease) in liabilities related to purchases of property and equipment and capitalized software		(355)	(1,022)
Restricted Cash [Abstract]
Cash, cash equivalents and restricted cash		$ 844,728	$ 885,481
[1]	The following table provides a reconciliation of cash, cash equivalents and restricted cash shown above to amounts reported within the condensed consolidated balance sheet as of March 31, 2019 and amounts previously reported within the condensed consolidated balance sheet in our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2018 (in thousands): March 31, 2019 March 31, 2018Cash and cash equivalents$645,610 $725,909Restricted cash included in prepaid expenses and other current assets1,973 4,332Restricted cash included in other non-current assets389 403Cash, cash equivalents and restricted cash$647,972 $730,644

DESCRIPTION OF BUSINESS AND BAS

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Company Information Groupon, Inc. and its subsidiaries, which commenced operations in October 2008, operate online local commerce marketplaces throughout the world that connect merchants to consumers by offering goods and services, generally at a discount. Customers access those marketplaces through our websites, primarily localized groupon.com sites in many countries, and our mobile applications. Our operations are organized into two segments: North America and International. See Note 13 , Segment Information . Unaudited Interim Financial Information We have prepared the accompanying condensed consolidated financial statements pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC") for interim financial reporting. These condensed consolidated financial statements are unaudited and, in our opinion, include all adjustments, consisting of normal recurring adjustments and accruals, necessary for a fair presentation of the condensed consolidated balance sheets, statements of operations and comprehensive income (loss), cash flows and stockholders' equity for the periods presented. Operating results for the periods presented are not necessarily indicative of the results to be expected for the full year ending December 31, 2019 . Certain information and disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") have been omitted in accordance with the rules and regulations of the SEC. These condensed consolidated financial statements and notes should be read in conjunction with the audited consolidated financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2018 , filed with the SEC on February 12, 2019. Principles of Consolidation The condensed consolidated financial statements include the accounts of Groupon, Inc. and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The condensed consolidated financial statements were prepared in accordance with U.S. GAAP and include the assets, liabilities, revenue and expenses of all wholly-owned subsidiaries and majority-owned subsidiaries over which we exercise control and a variable interest entity for which we have determined that we are the primary beneficiary. In the first quarter of 2019, we extended our arrangement through July 2022 with the strategic partner in the variable interest entity that we consolidate. Outside stockholders' interests in subsidiaries are shown on the condensed consolidated financial statements as Noncontrolling interests. Investments in entities in which we do not have a controlling financial interest are accounted for under the equity method, the fair value option, as available-for-sale securities or at cost adjusted for observable price changes and impairments, as appropriate. Adoption of New Accounting Standards We adopted the guidance in ASU 2016-02, Leases (Topic 842) on January 1, 2019. This ASU requires the recognition of lease assets and liabilities for operating leases, in addition to the finance lease assets and liabilities historically recorded on our condensed consolidated balance sheets. See Note 6 , Leases , for information on the impact of adopting Topic 842 on our accounting policies. We adopted the guidance in ASU 2018-07, Compensation - Stock Compensation (Topic 718) - Improvements to Nonemployee Share-Based Payment Accounting, on January 1, 2019. This ASU expands the scope to make the guidance for share-based payment awards to nonemployees consistent with the guidance for share-based payment awards to employees. The adoption of ASU 2018-07 did not have a material impact on the condensed consolidated financial statements. We adopted the guidance in ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This ASU requires entities in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40, Internal Use Software, to determine which costs to implement the service contract would be capitalized as an asset related to the service contract and which costs would be expensed. The requirements of ASU 2018-15 have been applied on a prospective basis to implementation costs incurred on or after January 1, 2019. As a result of the adoption of ASU 2018-15, we capitalized $0.9 million of implementation costs for the three months ended March 31, 2019 . Those capitalized costs are included within Other non-current assets on the condensed consolidated balance sheet as of March 31, 2019 . We have not recognized any amortization related to these implementation costs. We will amortize the implementation costs on a straight-line basis over the term of the associated hosting arrangement for each module or component of the related hosting arrangement when it is ready for its intended use. Amortization costs will be recorded in Selling, general and administrative expense on the condensed consolidated statements of operations. Reclassifications and Terminology Changes Certain reclassifications have been made to the condensed consolidated financial statements of prior periods and the accompanying notes to conform to the current period presentation. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires estimates and assumptions that affect the reported amounts and classifications of assets and liabilities, revenue and expenses, and the related disclosures of contingent liabilities in the condensed consolidated financial statements and accompanying notes. Estimates are used for, but not limited to, variable consideration from unredeemed vouchers, income taxes, initial valuation and subsequent impairment testing of goodwill and intangible assets, investments, customer refunds, contingent liabilities and the useful lives of property, equipment and software and intangible assets. Actual results could differ materially from those estimates.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS The following table summarizes goodwill activity by segment for the three months ended March 31, 2019 (in thousands): North America International Consolidated Balance as of December 31, 2018 $ 178,685 $ 146,806 $ 325,491 Foreign currency translation — (912 ) (912 ) Balance as of March 31, 2019 $ 178,685 $ 145,894 $ 324,579 The following table summarizes intangible assets as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Asset Category Gross Carrying Value Accumulated Amortization Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value Customer relationships $ 16,200 $ 13,050 $ 3,150 $ 16,200 $ 11,700 $ 4,500 Merchant relationships 22,004 5,208 16,796 21,554 4,105 17,449 Trade names 9,533 6,943 2,590 9,476 6,799 2,677 Developed technology 13,810 13,527 283 13,825 13,485 340 Patents 21,112 16,844 4,268 20,508 16,451 4,057 Other intangible assets 26,109 10,537 15,572 26,007 9,629 16,378 Total $ 108,768 $ 66,109 $ 42,659 $ 107,570 $ 62,169 $ 45,401 Amortization of intangible assets is computed using the straight-line method over their estimated useful lives, which range from 1 to 10 years. Amortization expense related to intangible assets was $3.9 million and $2.9 million for the three months ended March 31, 2019 and 2018 . As of March 31, 2019 , estimated future amortization expense related to intangible assets is as follows (in thousands): Remaining amounts in 2019 $ 10,179 2020 7,754 2021 7,017 2022 6,701 2023 5,543 Thereafter 5,465 Total $ 42,659

INVESTMENTS

INVESTMENTS	3 Months Ended
	Mar. 31, 2019
Schedule of Equity Method Investments [Abstract]
INVESTMENTS	3 . INVESTMENTS The following table summarizes investments as of March 31, 2019 and December 31, 2018 (dollars in thousands): March 31, 2019 Percent Ownership of Voting Stock December 31, 2018 Percent Ownership of Voting Stock Available-for-sale securities - redeemable preferred shares $ 10,394 19% to 25% $ 10,340 19% to 25% Fair value option investments 32,494 10% to 19% 73,902 10% to 19% Other equity investments (1) 24,025 1% to 19% 24,273 1% to 19% Total investments $ 66,913 $ 108,515 (1) Represents equity investments without readily determinable fair values. We have elected to record equity investments without readily determinable fair values at cost adjusted for observable price changes and impairments. There were no adjustments for observable price changes related to these investments since our adoption of ASU 2016-01, Financial Instruments (Topic 825-10) - Recognition and Measurement of Financial Assets and Financial Liabilities, on January 1, 2018. Available-for-Sale Securities - Redeemable Preferred Shares The following table summarizes amortized cost, gross unrealized gain, gross unrealized loss and fair value of redeemable preferred shares as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Amortized cost $ 9,961 $ 9,961 Gross unrealized gain 433 379 Gross unrealized loss — — Fair value $ 10,394 $ 10,340 Fair Value Option Investments In connection with the dispositions of controlling stakes in TMON Inc. ("TMON"), an entity based in the Republic of Korea, in May 2015 and Groupon India in August 2015, we obtained minority investments in Monster Holdings LP ("Monster LP") and in Nearbuy Pte Ltd. ("Nearbuy"), respectively. We have made an irrevocable election to account for both of those investments at fair value with changes in fair value reported in earnings. We elected to apply fair value accounting to those investments because we believe that fair value is the most relevant measurement attribute for those investments, and to reduce operational and accounting complexity. Our election to apply fair value accounting to those investments has and may continue to cause fluctuations in our earnings from period to period. We determined that the fair value of our investments in Monster LP and Nearbuy were $27.9 million and $4.6 million , respectively, as of March 31, 2019 and $69.4 million and $4.5 million , respectively, as of December 31, 2018 . Based on a discounted cash flow valuation, we recognized a $41.5 million loss due to changes in the fair value of our investment in Monster LP for the three months ended March 31, 2019 due to the revised cash flow projections provided by TMON in March 2019 and an increase in the discount rate applied to those forecasts. As of March 31, 2019 and December 31, 2018 , we applied discount rates of 26.0% and 21.0% in our discounted cash flow valuation. The increase in the discount rate applied as of March 31, 2019 was due to changes in the financial condition of TMON and the competitive environment in the Korean e-commerce industry which resulted in an increase to financial projection risk. The following table summarizes gains and losses due to changes in fair value of those investments for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Monster LP $ (41,459 ) $ (5,231 ) Nearbuy 51 198 Total $ (41,408 ) $ (5,033 )

SUPPLEMENTAL CONSOLIDATED BALAN

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION	3 Months Ended
	Mar. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION	SUPPLEMENTAL CONDENSED CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION The following table summarizes other income (expense), net for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Interest income $ 1,936 $ 1,509 Interest expense (5,691 ) (5,493 ) Changes in fair value of investments (41,408 ) (5,033 ) Foreign currency gains (losses), net (1,679 ) 1,398 Other (13 ) (896 ) Other income (expense), net $ (46,855 ) $ (8,515 ) The following table summarizes prepaid expenses and other current assets as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Merchandise inventories $ 30,652 $ 33,739 Prepaid expenses 27,517 28,209 Income taxes receivable 5,495 6,717 Other 19,022 19,450 Total prepaid expenses and other current assets $ 82,686 $ 88,115 The following table summarizes accrued merchant and supplier payables as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Accrued merchant payables $ 361,735 $ 371,279 Accrued supplier payables (1) 150,993 280,502 Total accrued merchant and supplier payables $ 512,728 $ 651,781 (1) Amounts include payables to suppliers of inventories and providers of shipping and fulfillment services. The following table summarizes accrued expenses and other current liabilities as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Refunds reserve $ 21,350 $ 27,957 Compensation and benefits 47,521 56,173 Accrued marketing 35,070 39,094 Customer credits 15,403 15,118 Income taxes payable 8,685 8,987 Deferred revenue 21,161 25,452 Current portion of lease obligations (1) 42,806 17,207 Other 64,064 77,046 Total accrued expenses and other current liabilities $ 256,060 $ 267,034 (1) Current portion of lease obligations as of March 31, 2019 includes $25.0 million of additional lease obligations that were recognized as a result of the adoption of Topic 842 on January 1, 2019. Refer to Note 6 , Leases , for additional information. The following table summarizes other non-current liabilities as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Contingent income tax liabilities $ 31,751 $ 39,858 Deferred rent (1) — 32,186 Deferred income taxes 3,880 6,619 Other 18,042 22,025 Total other non-current liabilities $ 53,673 $ 100,688 (1) Non-current operating lease liabilities as of March 31, 2019 are included within Operating lease obligations on the condensed consolidated balance sheet as a result of the adoption of Topic 842 on January 1, 2019. Refer to Note 6 , Leases , for additional information.

FINANCING ARRANGEMENTS

FINANCING ARRANGEMENTS	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
FINANCING ARRANGEMENTS	FINANCING ARRANGEMENTS Convertible Senior Notes On April 4, 2016, we issued $250.0 million in aggregate principal amount of convertible senior notes (the "Notes") in a private placement to A-G Holdings, L.P. ("AGH"). Michael Angelakis, the chairman and chief executive officer of Atairos Group, Inc. ("Atairos"), joined our Board of Directors in connection with the issuance of the Notes. Atairos controls the voting power of AGH. The net proceeds from this offering were $243.2 million after deducting issuance costs. The Notes bear interest at a rate of 3.25% per annum, payable annually in arrears on April 1 of each year, beginning on April 1, 2017. The Notes will mature on April 1, 2022, subject to earlier conversion or redemption. Each $1,000 of principal amount of the Notes initially is convertible into 185.1852 shares of common stock, which is equivalent to an initial conversion price of $5.40 per share, subject to adjustment upon the occurrence of specified events. Upon conversion, we can elect to settle the conversion value in cash, shares of our common stock, or any combination of cash and shares of our common stock. Holders of the Notes may convert their Notes at their option at any time until the close of business on the scheduled trading day immediately preceding the maturity date. In addition, if specified corporate events occur prior to the maturity date, we may be required to increase the conversion rate for holders who elect to convert based on the effective date of such event and the applicable stock price attributable to the event, as set forth in a table contained in the indenture governing the Notes (the "Indenture"). Based on the closing price of the common stock of $3.55 as of March 31, 2019 , the if-converted value of the Notes was less than the principal amount. With certain exceptions, upon a fundamental change (as defined in the Indenture), the holders of the Notes may require us to repurchase all or a portion of their Notes for cash at a purchase price equal to the principal amount plus accrued and unpaid interest. In addition, we may redeem the Notes, at our option, at a purchase price equal to the principal amount plus accrued and unpaid interest on or after April 1, 2020, if the closing sale price of the common stock exceeds 150% of the then-current conversion price for 20 or more trading days in the 30 consecutive trading-day period preceding the exercise of this redemption right. The Notes are senior unsecured obligations that rank equal in right of payment to all senior unsecured indebtedness and rank senior in right of payment to any indebtedness that is contractually subordinated to the Notes. The Indenture includes customary events of default. If an event of default, as defined in the Indenture, occurs and is continuing, the principal amount of the Notes and any accrued and unpaid interest may be declared immediately due and payable. In the case of bankruptcy or insolvency, the principal amount of the Notes and any accrued and unpaid interest would automatically become immediately due and payable. We have separated the Notes into their liability and equity components in the accompanying condensed consolidated balance sheets. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated conversion feature. The carrying amount of the equity component, representing the conversion option, was determined by deducting the fair value of the liability component from the principal amount of the Notes. The difference between the principal amount of the Notes and the liability component (the "debt discount") is amortized to interest expense at an effective interest rate of 9.75% over the term of the Notes. The equity component of the Notes is included in additional paid-in capital in the condensed consolidated balance sheets and is not remeasured as long as it continues to meet the conditions for equity classification. We incurred transaction costs of approximately $6.8 million related to the issuance of the Notes. Those transaction costs were allocated to the liability and equity components in the same manner as the allocation of the proceeds from the Notes. Transaction costs attributable to the liability component of $4.8 million were recorded as a debt discount in the condensed consolidated balance sheet and are being amortized to interest expense over the term of the Notes. Transaction costs attributable to the equity component of $2.0 million were recorded in stockholders' equity as a reduction of the equity component. The carrying amount of the Notes consisted of the following as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Liability component: Principal amount $ 250,000 $ 250,000 Less: debt discount (45,156 ) (48,331 ) Net carrying amount of liability component $ 204,844 $ 201,669 Net carrying amount of equity component $ 67,014 $ 67,014 The estimated fair value of the Notes as of March 31, 2019 and December 31, 2018 was $274.1 million and $257.1 million , and was determined using a lattice model. We classified the fair value of the Notes as a Level 3 measurement due to the lack of observable market data over fair value inputs such as our stock price volatility over the term of the Notes and our cost of debt. As of March 31, 2019 , the remaining term of the Notes is approximately 3 years. During the three months ended March 31, 2019 and 2018 , we recognized interest costs on the Notes as follows (in thousands): Three Months Ended March 31, 2019 2018 Contractual interest (3.25% of the principal amount per annum) $ 2,032 $ 2,032 Amortization of debt discount 3,175 2,866 Total $ 5,207 $ 4,898 Note Hedges and Warrants In May 2016, we purchased convertible note hedges with respect to our common stock for a cost of $59.1 million from certain bank counterparties. The convertible note hedges provide us with the right to purchase up to 46.3 million shares of our common stock at an initial strike price of $5.40 per share, which corresponds to the initial conversion price of the Notes, and are exercisable upon conversion of the Notes. The convertible note hedges are intended to reduce the potential economic dilution upon conversion of the Notes. The convertible note hedges are separate transactions and are not part of the terms of the Notes. Holders of the Notes do not have any rights with respect to the convertible note hedges. In May 2016, we also sold warrants for total cash proceeds of $35.5 million to certain bank counterparties. The warrants provide the counterparties with the right to purchase up to 46.3 million shares of our common stock at a strike price of $8.50 per share. The warrants expire on various dates between July 1, 2022 and August 26, 2022 and are exercisable on their expiration dates. The warrants are separate transactions and are not part of the terms of the Notes or convertible note hedges. Holders of the Notes and convertible note hedges do not have any rights with respect to the warrants. The amounts paid and received for the convertible note hedges and warrants were recorded in additional paid-in capital in the condensed consolidated balance sheets as of March 31, 2019 and December 31, 2018 . The convertible note hedges and warrants are not remeasured as long as they continue to meet the conditions for equity classification. The amounts paid for the convertible note hedges are tax deductible over the term of the Notes, while the proceeds received from the warrants are not taxable. Under the if-converted method, the shares of common stock underlying the conversion option in the Notes are included in the diluted earnings per share denominator and the interest expense on the Notes, net of tax, is added to the numerator. However, upon conversion, there will be no economic dilution from the Notes, as exercise of the convertible note hedges eliminates any dilution from the Notes that would have otherwise occurred when the price of our common stock exceeds the conversion price. Taken together, the purchase of the convertible note hedges and sale of warrants are intended to offset any actual dilution from the conversion of the Notes and to effectively increase the overall conversion price from $5.40 to $8.50 per share. Revolving Credit Agreement The amended and restated senior secured revolving credit agreement entered into in June 2016 (the "Amended and Restated Credit Agreement") provides for aggregate principal borrowings of up to $250.0 million and matures in June 2019. Borrowings under the Amended and Restated Credit Agreement bear interest, at our option, at a rate per annum equal to the Alternate Base Rate or Adjusted LIBO Rate (each as defined in the Amended and Restated Credit Agreement) plus an additional margin ranging between 0.50% and 2.25% . We are required to pay quarterly commitment fees ranging from 0.25% to 0.40% per annum of the average daily amount of unused commitments available under the Amended and Restated Credit Agreement. The Amended and Restated Credit Agreement also provides for the issuance of up to $45.0 million in letters of credit, provided that the sum of outstanding borrowings and letters of credit do not exceed the maximum funding commitment of $250.0 million . The Amended and Restated Credit Agreement is secured by substantially all of our tangible and intangible assets, including a pledge of 100% of the outstanding capital stock of substantially all of our direct and indirect domestic subsidiaries and 65% of the shares or equity interests of first-tier foreign subsidiaries and each U.S. entity whose assets substantially consist of capital stock and/or intercompany debt of one or more foreign subsidiaries, subject to certain exceptions. Certain of our domestic subsidiaries are guarantors under the Amended and Restated Credit Agreement. The Amended and Restated Credit Agreement contains various customary restrictive covenants that limit our ability to, among other things: incur additional indebtedness; make dividend and other restricted payments, including share repurchases; enter into sale and leaseback transactions; make investments, loans or advances; grant or incur liens on assets; sell assets; engage in mergers, consolidations, liquidations or dissolutions; and engage in transactions with affiliates. The Amended and Restated Credit Agreement requires us to maintain compliance with specified financial covenants, comprised of a minimum fixed charge coverage ratio, a maximum leverage ratio, a maximum senior secured indebtedness ratio and a minimum liquidity ratio, each as set forth in the Amended and Restated Credit Agreement. We are also required to maintain, as of the last day of each fiscal quarter, unrestricted cash of at least $400.0 million , including $200.0 million in accounts held with lenders under the Amended and Restated Credit Agreement or their affiliates. Non-compliance with these covenants may result in termination of the commitments under the Amended and Restated Credit Agreement and any then outstanding borrowings may be declared due and payable immediately. We have the right to terminate the Amended and Restated Credit Agreement or reduce the available commitments at any time. As of March 31, 2019 and December 31, 2018 , we have no borrowings and have outstanding letters of credit of $17.5 million and $19.2 million , under the Amended and Restated Credit Agreement.

LEASES

LEASES	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
LEASES	Adoption of ASC Topic 842, Leases On January 1, 2019, we adopted ASC Topic 842 using the modified retrospective transition method. Topic 842 requires the recognition of lease assets and liabilities for operating leases, in addition to the finance lease assets and liabilities previously recorded on our condensed consolidated balance sheets. Beginning on January 1, 2019, our condensed consolidated financial statements are presented in accordance with the revised policies, while prior period amounts are not adjusted and continue to be reported in accordance with our historical policies. The modified retrospective transition method required the cumulative effect, if any, of initially applying the guidance to be recognized as an adjustment to our accumulated deficit as of our adoption date. As a result of adopting Topic 842, we recognized additional lease assets and liabilities of $109.6 million as of January 1, 2019. The discount rate used to calculate that adjustment was the rate implicit in the lease, unless that rate was not readily determinable. For leases for which the rate was not readily determinable, the discount rate used was our incremental borrowing rate as of the adoption date, January 1, 2019. There was no cumulative effect adjustment to our accumulated defi cit as a result of initially applying the guidance. We elected the package of practical expedients permitted under the transition guidance within Topic 842, which allowed us to carry forward prior conclusions about lease identification, classification and initial direct costs for leases entered into prior to adoption of Topic 842. Additionally, we elected to not separate lease and non-lease components for all of our leases. For leases with a term of 12 months or less, we elected the short-term lease exemption, which allowed us to not recognize right-of-use assets or lease liabilities for qualifying leases existing at transition and new leases we may enter into in the future. General Description of Leases We have entered into various non-cancelable operating lease agreements for our offices and data centers and non-cancelable finance lease agreements for property and equipment. We classify leases at their commencement as either operating or finance leases and may receive renewal or expansion options, rent holidays and leasehold improvement or other incentives on certain lease agreements. Our operating leases primarily consist of leases for real estate throughout the world with lease expirations between 2019 and 2026. These arrangements typically do not transfer ownership of the underlying asset as we do not assume, nor do we intend to assume, the risks and rewards of ownership. Our finance leases are related to purchases of property and equipment, primarily computer hardware, with expirations between 2019 and 2023. We recognize a right-of-use asset and lease liability for all of our leases at the commencement of the lease. Lease liabilities are measured based on the present value of the minimum lease payments discounted by a rate determined as of the date of commencement. Right-of-use assets are measured based on the lease liability adjusted for any initial direct costs, prepaid rent, or lease incentives. Minimum lease payments made under operating and finance leases are apportioned between interest expense and a reduction of the related operating and finance lease obligations. The interest expense on operating leases is presented within Selling, general and administrative expense on the condensed consolidated statements of operations and the related operating lease obligation is presented within Accrued expenses and other current liabilities and Operating lease obligations on the condensed consolidated balance sheets. The interest expense on finance leases is presented within Other income (expense), net on the condensed consolidated statements of operations and the related finance lease obligation is presented within Accrued expenses and other current liabilities and Other non-current liabilities on the condensed consolidated balance sheets. We have also subleased certain office facilities under operating lease agreements, with expirations between 2019 and 2026. We recognize sublease rentals on a straight-line basis over their respective lease terms. The following summarizes right-of-use assets as of March 31, 2019 (in thousands): March 31, 2019 Right-of-use assets - operating leases $ 109,555 Right-of-use assets - finance leases (1) 32,196 Total right-of-use assets, gross 141,751 Less: accumulated depreciation and amortization (13,197 ) Right-of-use assets, net $ 128,554 (1) Right-of-use assets for finance leases are included in Property, equipment and software, net on the condensed consolidated balance sheet. Related Party Sublease Agreement On December 28, 2016, we entered into a sublease for portions of our office space at 600 West Chicago to Uptake, Inc. ("Uptake"), a Lightbank LLC ("Lightbank") portfolio company. Eric Lefkofsky, our co-founder and Chairman of the Board, is a co-founder and owns a significant equity interest in Lightbank. The sublease was negotiated on an arm’s-length basis and is a market rate transaction on terms that we believe are no less favorable than would have been reached with an unrelated third party. The sublease extends through January 31, 2026 and the sublease rentals over that term total approximately $18.2 million . Pursuant to our related party transaction policy, our Audit Committee approved the sublease. During the three months ended March 31, 2019 and 2018 , we recognized $0.7 million and $0.5 million , in income from the sublease. Significant Assumptions and Judgments Significant judgment is required when determining whether a contract is or contains a lease. We review contracts to determine whether the language conveys the right to control the use of an identified asset for a period of time in exchange for consideration. As discussed above, the present value of minimum lease payments is used in determining the value of our operating and finance leases. The discount rate used to calculate the present value for lease payments is the rate implicit in the lease, unless that rate cannot be readily determined. For leases in which the rate implicit in the lease is not readily determinable, the discount rate is our incremental borrowing rate, which is determined based on information available at lease commencement and is equal to the rate of interest that we would have to pay to borrow on a collateralized basis over a similar term in an amount equal to the lease payments in a similar economic environment. The discount rate used for our lease obligations as of March 31, 2019 and January 1, 2019 ranged from 1.5% to 6.9% . As of March 31, 2019 , the weighted-average remaining lease term for our finance leases and operating leases was 2.04 years and 5.41 years. As of March 31, 2019 , the weighted-average discount rate for our finance leases and operating leases was 5.0% and 5.8% . The following table summarizes our lease cost and sublease income for the three months ended March 31, 2019 (in thousands): Three Months Ended March 31, 2019 Financing lease cost: Amortization of right-of-use assets $ 6,756 Interest on lease liabilities 307 Total finance lease cost 7,063 Operating lease cost 8,474 Variable lease cost 892 Short-term lease cost 41 Sublease income, gross (1,312 ) Total lease cost $ 15,158 As of March 31, 2019 , the future payments under finance leases and operating leases for each of the next five years and thereafter are as follows (in thousands): Finance Leases Operating Leases Remaining in 2019 $ 11,373 $ 26,612 2020 7,654 31,932 2021 4,806 26,998 2022 715 26,114 2023 12 21,917 Thereafter — 32,600 Total minimum lease payments 24,560 166,173 Less: Amount representing interest (1,272 ) (24,964 ) Present value of net minimum lease payments 23,288 141,209 Less: Current portion of lease obligations (12,596 ) (30,210 ) Total long-term lease obligations $ 10,692 $ 110,999 As of March 31, 2019 , the future amounts due under subleases for each of the next five years and thereafter are as follows (in thousands): Subleases Remaining in 2019 $ 3,905 2020 5,027 2021 5,065 2022 5,103 2023 4,385 Thereafter 4,891 Total future sublease income $ 28,376 The following table summarizes supplemental cash flow information on our leasing obligations for the three months ended March 31, 2019 (in thousands): Three Months Ended March 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 307 Operating cash flows from operating leases (6,481 ) Financing cash flows from finance leases (6,756 )

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Our purchase obligations as of March 31, 2019 did not materially change from the amounts set forth in our 2018 Annual Report on Form 10-K. Legal Matters and Other Contingencies From time to time, we are party to various legal proceedings incident to the operation of our business. For example, we currently are involved in proceedings brought by former employees and merchants, intellectual property infringement suits, customer lawsuits, consumer class actions and suits alleging, among other things, violations of state consumer protection or privacy laws. In addition, third parties have from time to time claimed, and others may claim in the future, that we have infringed their intellectual property rights. We are subject to intellectual property disputes, including patent infringement claims, and expect that we will continue to be subject to intellectual property infringement claims as our services expand in scope and complexity. In the past, we have litigated such claims, and we are presently involved in several patent infringement and other intellectual property-related claims, including pending litigation or trademark disputes relating to, for example, our Goods category, some of which could involve potentially substantial claims for damages or injunctive relief. We may also become more vulnerable to third-party claims as laws such as the Digital Millennium Copyright Act are interpreted by the courts, and we become subject to laws in jurisdictions where the underlying laws with respect to the potential liability of online intermediaries are either unclear or less favorable. We believe that additional lawsuits alleging that we have violated patent, copyright or trademark laws will be filed against us. Intellectual property claims, whether meritorious or not, are time consuming and often costly to resolve, could require expensive changes in our methods of doing business or the goods we sell, or could require us to enter into costly royalty or licensing agreements. We also are subject to consumer claims or lawsuits relating to alleged violations of consumer protection or privacy rights and statutes, some of which could involve potentially substantial claims for damages, including statutory or punitive damages. Consumer and privacy related claims or lawsuits, whether meritorious or not, could be time consuming, result in costly litigation, damage awards, fines and penalties, injunctive relief or increased costs of doing business through adverse judgment or settlement, or require us to change our business practices, sometimes in expensive ways. We are also subject to, or in the future may become subject to, a variety of regulatory inquiries, audits, and investigations across the jurisdictions where we conduct our business, including, for example, inquiries related to consumer protection, employment matters and/or hiring practices, marketing practices, tax, unclaimed property and privacy rules and regulations. Any regulatory actions against us, whether meritorious or not, could be time consuming, result in costly litigation, damage awards, fines and penalties, injunctive relief or increased costs of doing business through adverse judgment or settlement, require us to change our business practices in expensive ways, require significant amounts of management time, result in the diversion of significant operational resources or otherwise harm our business. We establish an accrued liability for loss contingencies related to legal and regulatory matters when the loss is both probable and reasonably estimable. Those accruals represent management's best estimate of probable losses and, in such cases, there may be an exposure to loss in excess of the amounts accrued. For certain of the matters described above, there are inherent and significant uncertainties based on, among other factors, the stage of the proceedings, developments in the applicable facts of law, or the lack of a specific damage claim. However, we believe that the amount of reasonably possible losses in excess of the amounts accrued for those matters would not have a material adverse effect on our business, condensed consolidated financial position, results of operations or cash flows. Our accrued liabilities for loss contingencies related to legal and regulatory matters may change in the future as a result of new developments, including, but not limited to, the occurrence of new legal matters, changes in the law or regulatory environment, adverse or favorable rulings, newly discovered facts relevant to the matter, or changes in the strategy for the matter. Regardless of the outcome, litigation and other regulatory matters can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors. Indemnifications In connection with the disposition of our operations in Latin America in the first quarter of 2017, we recorded $5.4 million in indemnification liabilities for certain tax and other matters upon the closing of the transactions as an adjustment to the net loss on the dispositions within discontinued operations at their fair value. We estimated the indemnification liabilities using a probability-weighted expected cash flow approach. During the first quarter of 2019, we decreased our indemnification liabilities due to the expiration of certain indemnification obligations. The resulting benefit of $2.2 million is recorded within Income (loss) from discontinued operations on the condensed consolidated statement of operations for the three months ended March 31, 2019. Our remaining indemnification liabilities were $3.2 million as of March 31, 2019 . We estimate that the total amount of obligations that are reasonably possible to arise under the indemnifications in excess of amounts accrued as of March 31, 2019 is approximately $13.3 million . In the normal course of business to facilitate transactions related to our operations, we indemnify certain parties, including employees, lessors, service providers, merchants, and counterparties to investment agreements and asset and stock purchase agreements with respect to various matters. We have agreed to hold certain parties harmless against losses arising from a breach of representations or covenants, or other claims made against those parties. These agreements may limit the time within which an indemnification claim can be made and the amount of the claim. We are also subject to increased exposure to various claims as a result of our divestitures and acquisitions, particularly in cases where we are entering into new businesses in connection with such acquisitions. We may also become more vulnerable to claims as we expand the range and scope of our services and are subject to laws in jurisdictions where the underlying laws with respect to potential liability are either unclear or less favorable. In addition, we have entered into indemnification agreements with our officers, directors and underwriters, and our bylaws contain similar indemnification obligations that cover officers, directors, employees and other agents. Except as noted above, it is not possible to determine the maximum potential amount under these indemnification agreements due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement. Historically, any payments that we have made under these agreements have not had a material impact on the operating results, financial position or cash flows.
Legal Matters and Contingencies [Text Block]	Legal Matters and Other Contingencies From time to time, we are party to various legal proceedings incident to the operation of our business. For example, we currently are involved in proceedings brought by former employees and merchants, intellectual property infringement suits, customer lawsuits, consumer class actions and suits alleging, among other things, violations of state consumer protection or privacy laws. In addition, third parties have from time to time claimed, and others may claim in the future, that we have infringed their intellectual property rights. We are subject to intellectual property disputes, including patent infringement claims, and expect that we will continue to be subject to intellectual property infringement claims as our services expand in scope and complexity. In the past, we have litigated such claims, and we are presently involved in several patent infringement and other intellectual property-related claims, including pending litigation or trademark disputes relating to, for example, our Goods category, some of which could involve potentially substantial claims for damages or injunctive relief. We may also become more vulnerable to third-party claims as laws such as the Digital Millennium Copyright Act are interpreted by the courts, and we become subject to laws in jurisdictions where the underlying laws with respect to the potential liability of online intermediaries are either unclear or less favorable. We believe that additional lawsuits alleging that we have violated patent, copyright or trademark laws will be filed against us. Intellectual property claims, whether meritorious or not, are time consuming and often costly to resolve, could require expensive changes in our methods of doing business or the goods we sell, or could require us to enter into costly royalty or licensing agreements. We also are subject to consumer claims or lawsuits relating to alleged violations of consumer protection or privacy rights and statutes, some of which could involve potentially substantial claims for damages, including statutory or punitive damages. Consumer and privacy related claims or lawsuits, whether meritorious or not, could be time consuming, result in costly litigation, damage awards, fines and penalties, injunctive relief or increased costs of doing business through adverse judgment or settlement, or require us to change our business practices, sometimes in expensive ways. We are also subject to, or in the future may become subject to, a variety of regulatory inquiries, audits, and investigations across the jurisdictions where we conduct our business, including, for example, inquiries related to consumer protection, employment matters and/or hiring practices, marketing practices, tax, unclaimed property and privacy rules and regulations. Any regulatory actions against us, whether meritorious or not, could be time consuming, result in costly litigation, damage awards, fines and penalties, injunctive relief or increased costs of doing business through adverse judgment or settlement, require us to change our business practices in expensive ways, require significant amounts of management time, result in the diversion of significant operational resources or otherwise harm our business. We establish an accrued liability for loss contingencies related to legal and regulatory matters when the loss is both probable and reasonably estimable. Those accruals represent management's best estimate of probable losses and, in such cases, there may be an exposure to loss in excess of the amounts accrued. For certain of the matters described above, there are inherent and significant uncertainties based on, among other factors, the stage of the proceedings, developments in the applicable facts of law, or the lack of a specific damage claim. However, we believe that the amount of reasonably possible losses in excess of the amounts accrued for those matters would not have a material adverse effect on our business, condensed consolidated financial position, results of operations or cash flows. Our accrued liabilities for loss contingencies related to legal and regulatory matters may change in the future as a result of new developments, including, but not limited to, the occurrence of new legal matters, changes in the law or regulatory environment, adverse or favorable rulings, newly discovered facts relevant to the matter, or changes in the strategy for the matter. Regardless of the outcome, litigation and other regulatory matters can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors.

STOCKHOLDERS' EQUITY AND COMPEN

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS	STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS Common Stock Pursuant to our restated certificate of incorporation, the Board has the authority to issue up to a total of 2,010,000,000 shares of common stock. Each holder of common stock is entitled to one vote per share on any matter that is submitted to a vote of stockholders. In addition, holders of our common stock will vote as a single class of stock on any matter that is submitted to a vote of stockholders. Share Repurchase Program In May 2018, the Board authorized us to repurchase up to $300.0 million of our common stock under our share repurchase program. During the three months ended March 31, 2019 , we repurchased 4,407,995 shares for an aggregate purchase price of $15.1 million (including fees and commissions) under our repurchase program. No amounts were repurchased under the prior share repurchase program during the three months ended March 31, 2018 . As of March 31, 2019 , up to $275.0 million of common stock remained available for purchase under our program. The timing and amount of share repurchases, if any, will be determined based on market conditions, limitations under the Amended and Restated Credit Agreement, share price and other factors, and the share repurchase program may be terminated at any time. Groupon, Inc. Stock Plans The Groupon, Inc. Stock Plans (the "Plans") are administered by the Compensation Committee of the Board (the "Compensation Committee"). As of March 31, 2019 , 42,997,198 shares of common stock were available for future issuance under the Plans. The stock-based compensation expense related to stock awards issued under the Plans and acquisition-related awards are presented within the following line items of the condensed consolidated statements of operations for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Cost of revenue $ 378 $ 396 Marketing 1,425 1,794 Selling, general and administrative 14,608 17,088 Other income (expense), net — 48 Total stock-based compensation expense $ 16,411 $ 19,326 We capitalized $1.3 million and $1.7 million of stock-based compensation for the three months ended March 31, 2019 and 2018 , in connection with internally-developed software. As of March 31, 2019 , $129.7 million of unrecognized compensation costs related to unvested stock-based compensation awards are expected to be recognized over a remaining weighted-average period of 1.5 years. Employee Stock Purchase Plan We are authorized to grant up to 10,000,000 shares of common stock under our employee stock purchase plan ("ESPP"). For the three months ended March 31, 2019 and 2018 , 719,297 and 746,773 shares of common stock were issued under the ESPP. Restricted Stock Units The restricted stock units granted under the Plans generally have vesting periods between one and four years and are amortized on a straight-line basis over their requisite service period. Additionally, we are required to issue restricted stock units to settle amounts that exceed targeted bonus amounts under our primary bonus plans. We account for those obligations, if any, as liability-classified awards with performance conditions. The table below summarizes restricted stock unit activity under the Plans for the three months ended March 31, 2019 : Restricted Stock Units Weighted-Average Grant Date Fair Value (per unit) Unvested at December 31, 2018 26,623,432 $ 4.47 Granted 5,759,900 3.89 Vested (3,382,842 ) 4.43 Forfeited (2,828,751 ) 4.39 Unvested at March 31, 2019 26,171,739 4.35 Performance Share Units We grant performance share units under the Plans that vest in shares of our common stock upon the achievement of financial and operational targets specified in the respective award agreement ("Performance Share Units"). During the three months ended March 31, 2019, we also granted performance share units that will vest if our average daily closing stock price is equal to or greater than $6.00 per share over a period of 30 consecutive trading days prior to December 31, 2022 or if a change in control occurs during the performance period at the specified stock price (and on a proportional basis for a change in control price between the grant date price and the specified stock price) ("Market-based Performance Share Units"). We determined these awards are subject to a market condition, and therefore we used a Monte Carlo simulation to calculate the grant date fair value of the awards and the related derived service period over which we will recognize the expense. The key inputs used in the Monte Carlo simulation were the risk-free rate, our volatility of 49.8% and our cost of equity of 12.8% . All of our performance share awards are subject to both continued employment through the performance period dictated by the award and certification by the Compensation Committee that the specified performance conditions have been achieved. The table below summarizes Performance Share Unit activity under the Plans for the three months ended March 31, 2019 : Performance Share Units Weighted-Average Grant Date Fair Value (per unit) Market-based Performance Share Units Weighted-Average Grant Date Fair Value (per unit) Unvested at December 31, 2018 3,431,918 $ 4.90 — $ — Granted 4,013,126 3.96 8,486,708 3.03 Vested (777,573 ) 4.88 — — Forfeited (2,191,878 ) 4.90 — — Unvested at March 31, 2019 4,475,593 4.06 8,486,708 3.03 The maximum number of common shares issuable upon vesting of the Performance Share Units and Market-based Performance Share Units granted in 2019 was 8,026,252 and 8,486,708 shares, respectively, as of March 31, 2019 . Stock Options The exercise price of stock options granted is equal to the fair value of the underlying stock on the date of grant. The contractual term for stock options expires ten years from the grant date. Stock options generally vest over a three - or four -year period, with 25% of the awards vesting after one year and the remainder of the awards vesting on a monthly or quarterly basis thereafter. We did not grant any stock options during the three months ended March 31, 2019 . The table below summarizes stock option activity for the three months ended March 31, 2019 : Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) (1) Outstanding and exercisable at December 31, 2018 212,787 $ 1.80 1.37 $ 298 Exercised (12,500 ) 0.68 Outstanding and exercisable at March 31, 2019 200,287 $ 1.85 1.14 $ 340 (1) The aggregate intrinsic value of options outstanding and exercisable represents the total pretax intrinsic value (the difference between the fair value of our stock on the last day of each period and the exercise price, multiplied by the number of options where the fair value exceeds the exercise price) that would have been received by the option holders had all option holders exercised their options as of March 31, 2019 and December 31, 2018 .

REVENUE RECOGNITION

REVENUE RECOGNITION	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION Refer to Note 13 , Segment Information , for revenue summarized by reportable segment and category for the three months ended March 31, 2019 and 2018 . Contract Balances A substantial majority of our deferred revenue relates to product sales for which revenue will be recognized as the products are delivered to customers, generally within one week following the balance sheet date. Our deferred revenue was $21.2 million and $25.5 million as of March 31, 2019 and December 31, 2018 . The amount of revenue recognized for the three months ended March 31, 2019 that was included in the deferred revenue balance at the beginning of the period was $25.3 million . The following table summarizes the activity in the liability for customer credits for the three months ended March 31, 2019 (in thousands): Customer Credits Balance as of December 31, 2018 $ 15,118 Credits issued 27,803 Credits redeemed (1) (25,020 ) Breakage revenue recognized (2,560 ) Foreign currency translation 62 Balance as of March 31, 2019 $ 15,403 (1) Customer credits can be redeemed through our online marketplaces for goods or services provided by a third-party merchant or for merchandise inventory sold by us. When customer credits are redeemed for goods or services provided by a third-party merchant, service revenue is recognized on a net basis as the difference between the carrying amount of the customer credit liability derecognized and the amount due to the merchant for the related transaction. When customer credits are redeemed for merchandise inventory sold by us, product revenue is recognized on a gross basis equal to the amount of the customer credit liability derecognized. Customer credits are typically used within one year of issuance. Costs of Obtaining Contracts Incremental costs to obtain contracts with third-party merchants, such as sales commissions, are deferred and recognized over the expected period of the merchant arrangement, generally from 12 to 18 months. Those costs are classified within Selling, general and administrative expense in the condensed consolidated statements of operations. As of March 31, 2019 and December 31, 2018 , we had deferred contract acquisition costs of $2.8 million and $2.9 million , respectively, recorded within Prepaid expenses and other current assets, and $10.5 million and $11.3 million , respectively, recorded within Other non-current assets. During the three months ended March 31, 2019 and 2018 , we amortized $5.4 million and $6.8 million of deferred contract acquisition costs and did not recognize any impairment losses in relation to the deferred costs. Variable Consideration for Unredeemed Vouchers In our International segment and, to a lesser extent, in our North America segment, our merchant agreements have redemption payment terms, under which the merchant is not paid its share of the sale price for a voucher sold through one of our online marketplaces until the customer redeems the related voucher. If the customer does not redeem a voucher with such merchant payment terms, we retain all of the gross billings for that voucher, rather than retaining only our net commission. We estimate the variable consideration from vouchers that will not ultimately be redeemed using our historical voucher redemption experience and recognize that amount as revenue at the time of sale. We only recognize amounts in variable consideration when we believe it is probable that a significant reversal of revenue will not occur in future periods, which requires us to make significant estimates of future redemptions. If actual redemptions differ from our estimates, the effects could be material to the condensed consolidated financial statements. As of March 31, 2019 and December 31, 2018, we constrained $13.3 million and $13.7 million in revenue from unredeemed vouchers that we may recognize in future periods when we determine it is probable that a significant amount of that revenue will not be subsequently reversed.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our income tax provision for interim periods is determined using an estimate of our annual effective tax rate, adjusted for discrete items. For the three months ended March 31, 2019 , we recorded an income tax benefit from continuing operations of $3.5 million on a pretax loss from continuing operations of $44.7 million . For the three months ended March 31, 2018 , we recorded an income tax benefit from continuing operations of $2.3 million on a pretax loss from continuing operations of $5.1 million . Our U.S. Federal income tax rate is 21% . The primary factor impacting the effective tax rate for the three months ended March 31, 2019 was the pretax losses incurred in jurisdictions that have valuation allowances against their net deferred tax assets and the reversal of reserves for uncertain tax positions due to the closure of a tax audit . We expect that our consolidated effective tax rate in future periods will continue to differ significantly from t he U.S. federal income tax rate as a result of our tax obligations in jurisdictions with profits and valuation allowances in jurisdictions with losses. The effective tax rate for the three months ended March 31, 2018 reflected a $6.4 million income tax benefit resulting from the impact of Topic 606 on intercompany activity in certain foreign jurisdictions, partially offset by pretax losses incurred in jurisdictions that have valuation allowances against their net deferred tax assets. We are currently undergoing income tax audits in multiple jurisdictions. It is likely that the examination phase of some of those audits will conclude in the next 12 months. There are many factors, including factors outside of our control, which influence the progress and completion of those audits. We are subject to claims for tax assessments by foreign jurisdictions, including a proposed assessment for $108.5 million . We believe that the assessment, which primarily relates to transfer pricing on transactions occurring in 2011, is without merit and we intend to vigorously defend ourselves in that matter. In addition to any potential increases in our liabilities for uncertain tax positions from the ultimate resolution of that assessment, we believe that it is reasonably possible that reductions of up to $24.3 million in unrecognized tax benefits may occur within the 12 months following March 31, 2019 upon closing of income tax audits or the expiration of applicable statutes of limitations. In general, it is our practice and intention to reinvest the earnings of our non-U.S. subsidiaries in those operations. Additionally, while we did not incur the deemed repatriation tax, an actual repatriation from our non-U.S. subsidiaries could be subject to foreign and U.S. state income taxes. Aside from limited exceptions for which the related deferred tax liabilities recognized as of March 31, 2019 and December 31, 2018 are immaterial, we do not intend to distribute earnings of foreign subsidiaries for which we have an excess of the financial reporting basis over the tax basis of our investments and therefore have not recorded any deferred taxes related to such amounts. The actual tax cost resulting from a distribution would depend on income tax laws and circumstances at the time of distribution. Determination of the amount of unrecognized deferred tax liability related to the excess of the financial reporting basis over the tax basis of our foreign subsidiaries is not practical due to the complexities associated with the calculation. On July 24, 2018, the Ninth Circuit Court of Appeals issued an opinion in Altera Corp. v. Commissioner requiring related parties in an intercompany cost-sharing arrangement to share expenses related to stock-based compensation. This opinion reversed an earlier decision of the United States Tax Court. On August 7, 2018, the Ninth Circuit Court of Appeals withdrew its July 24, 2018 opinion. We are continuing to monitor the status of this case; however, we currently do not expect that it will have a material impact on our provision for income taxes for the year ending December 31, 2019 due to the valuation allowances against our net deferred tax assets in the related jurisdictions.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Fair value is defined under U.S. GAAP as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value is a market-based measurement that is determined based on assumptions that market participants would use in pricing an asset or a liability. To increase the comparability of fair value measures, the following hierarchy prioritizes the inputs in valuation methodologies used to measure fair value: Level 1 - Measurements that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 - Measurements that include other inputs that are directly or indirectly observable in the marketplace. Level 3 - Measurements derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. These fair value measurements require significant judgment. In determining fair value, we use various valuation approaches within the fair value measurement framework. The valuation methodologies used for our assets and liabilities measured at fair value and their classification in the valuation hierarchy are summarized below: Fair value option investments and available-for-sale securities. To determine the fair value of our fair value option investments each period, we first estimate the fair value of each entity in its entirety. We primarily use the discounted cash flow method, which is an income approach, to estimate the fair value of the entities. The key inputs to determining fair values under that approach are cash flow forecasts and discount rates. We also use a market approach valuation technique, which is based on market multiples of guideline companies, to determine the fair value of each entity. The discounted cash flow and market multiple valuations are then evaluated and weighted to determine the amount that is most representative of the fair value of each entity. Once we determine the fair value of each entity, we then determine the fair value of our specific investments in those entities. The entities have complex capital structures, so we apply an option-pricing model that considers the liquidation preferences of each entity's respective classes of ownership interests to determine the fair value of our investment in each entity. We also have investments in redeemable preferred shares and had investments in convertible debt securities issued by nonpublic entities. We measure the fair value of those available-for-sale securities using the discounted cash flow method. We have classified our fair value option investments and our investments in available-for-sale securities as Level 3 due to the lack of observable market data over fair value inputs such as cash flow projections and discount rates. Increases in projected cash flows and decreases in discount rates contribute to increases in the estimated fair values of the fair value option investments and available-for-sale securities, whereas decreases in projected cash flows and increases in discount rates contribute to decreases in their fair values. Contingent consideration. We are subject to a contingent consideration arrangement to transfer a maximum payout in cash of $2.5 million to the former owners of a business acquired on April 30, 2018. Liabilities for contingent consideration are measured at fair value each reporting period, with the acquisition-date fair value included as part of the consideration transferred in the related business combination and subsequent changes in fair value recorded in earnings within Selling, general and administrative expense on the condensed consolidated statements of operations. We use an income approach to value contingent consideration obligations based on the present value of probability-weighted future cash flows. We classify the contingent consideration liabilities as Level 3 due to the lack of relevant observable market data over fair value inputs such as probability-weighting of payment outcomes. The following tables summarize assets that are measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 (in thousands): Fair Value Measurement at Reporting Date Using March 31, 2019 Quoted Prices in Active Markets for Significant Other Significant Assets: Fair value option investments $ 32,494 $ — $ — $ 32,494 Available-for-sale securities - redeemable preferred shares 10,394 — — 10,394 Liabilities: Contingent consideration 1,586 — — 1,586 Fair Value Measurement at Reporting Date Using December 31, 2018 Quoted Prices in Active Markets for Significant Other Significant Assets: Fair value option investments $ 73,902 $ — $ — $ 73,902 Available-for-sale securities - redeemable preferred shares 10,340 — — 10,340 Liabilities: Contingent consideration 1,529 — — 1,529 The following table provides a roll-forward of the fair value of recurring Level 3 fair value measurements for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Assets Fair value option investments: Beginning Balance $ 73,902 $ 82,966 Total gains (losses) included in earnings (41,408 ) (5,033 ) Ending Balance $ 32,494 $ 77,933 Unrealized gains (losses) still held (1) $ (41,408 ) $ (5,033 ) Available-for-sale securities Convertible debt securities: Beginning Balance $ — $ 11,354 Total gains (losses) included in other comprehensive income (loss) — (501 ) Total gains (losses) included in earnings (2) — 217 Ending Balance $ — $ 11,070 Unrealized gains (losses) still held (1) $ — $ (284 ) Redeemable preferred shares: Beginning Balance $ 10,340 $ 15,431 Total gains (losses) included in other comprehensive income (loss) 54 — Impairment included in earnings — (855 ) Ending Balance $ 10,394 $ 14,576 Unrealized gains (losses) still held (1) $ 54 $ (855 ) Liabilities Contingent Consideration: Beginning Balance $ 1,529 $ — Total losses (gains) included in earnings 22 — Foreign currency translation 35 — Ending Balance $ 1,586 $ — Unrealized gains (losses) still held (1) $ 22 $ — (1) Represents the unrealized gains or losses recorded in earnings and/or other comprehensive income (loss) during the period for assets and liabilities classified as Level 3 that are still held (or outstanding) at the end of the period. (2) Represents a gain at maturity of a previously impaired convertible debt security, accretion of interest income and changes in the fair value of an embedded derivative. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Certain assets and liabilities are measured at fair value on a nonrecurring basis, including assets that are written down to fair value as a result of an impairment. We did not record any significant nonrecurring fair value measurements after initial recognition for the three months ended March 31, 2019 and 2018 . Estimated Fair Value of Financial Assets and Liabilities Not Measured at Fair Value Our financial instruments not carried at fair value consist primarily of accounts receivable, restricted cash, accounts payable, accrued merchant and supplier payables and accrued expenses. The carrying values of those assets and liabilities approximate their respective fair values as of March 31, 2019 and December 31, 2018 due to their short-term nature.

INCOME (LOSS) PER SHARE

INCOME (LOSS) PER SHARE	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
INCOME (LOSS) PER SHARE	INCOME (LOSS) PER SHARE Basic net income (loss) per share is computed using the weighted-average number of common shares outstanding during the period. Diluted net income (loss) per share is computed using the weighted-average number of common shares and the effect of potentially dilutive securities outstanding during the period. Potentially dilutive securities include stock options, restricted stock units, performance share units, ESPP shares, warrants and convertible senior notes. If dilutive, those potentially dilutive securities are reflected in diluted net income (loss) per share by application of the treasury stock method, except for the convertible senior notes, which are subject to the if-converted method. The following table sets forth the computation of basic and diluted net income (loss) per share of common stock for the three months ended March 31, 2019 and 2018 (in thousands, except share and per share amounts): Three Months Ended March 31, 2019 2018 Basic and diluted net income (loss) per share: Numerator Net income (loss) - continuing operations $ (41,170 ) $ (2,795 ) Less: Net income (loss) attributable to noncontrolling interests 3,479 4,093 Net income (loss) attributable to common stockholders - continuing operations (44,649 ) (6,888 ) Net income (loss) attributable to common stockholders - discontinued operations 2,162 — Net income (loss) attributable to common stockholders $ (42,487 ) $ (6,888 ) Denominator Weighted-average common shares outstanding 570,095,128 561,735,937 Basic and diluted net income (loss) per share: Continuing operations $ (0.08 ) $ (0.01 ) Discontinued operations 0.01 0.00 Basic and diluted net income (loss) per share $ (0.07 ) $ (0.01 ) The following weighted-average potentially dilutive instruments are not included in the diluted net income (loss) per share calculations above because they would have had an antidilutive effect on the net income (loss) per share from continuing operations: Three Months Ended March 31, 2019 2018 Restricted stock units 27,088,851 28,033,489 Other stock-based compensation awards 1,752,744 3,212,026 Convertible senior notes 46,296,300 46,296,300 Warrants 46,296,300 46,296,300 Total 121,434,195 123,838,115 We had outstanding performance share units as of March 31, 2019 and 2018 that were eligible to vest into shares of common stock subject to the achievement of specified performance conditions. Contingently issuable shares are excluded from the computation of diluted earnings per share if, based on current period results, the shares would not be issuable if the end of the reporting period were the end of the contingency period. There were up to 16,512,960 and 3,283,114 shares of common stock issuable upon vesting of outstanding performance share units as of March 31, 2019 and 2018 that were excluded from the table above as the performance conditions were not satisfied as of the end of the respective periods.

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION The segment information reported in the tables below reflects the operating results that are regularly reviewed by our chief operating decision maker to assess performance and make resource allocation decisions. Our operations are organized into two segments: North America and International. The following table summarizes revenue by reportable segment and category for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 North America Service revenue: Local $ 180,377 $ 187,411 Goods 3,127 4,874 Travel 18,941 20,084 Product revenue - Goods 154,720 180,887 Total North America revenue (1) 357,165 393,256 International Service revenue: Local 73,190 74,578 Goods 1,455 3,414 Travel 8,737 11,436 Product revenue - Goods 137,863 143,856 Total International revenue (1) $ 221,245 $ 233,284 (1) North America includes revenue from the United States of $348.8 million and $385.4 million for the three months ended March 31, 2019 and 2018 . International includes revenue from the United Kingdom of $81.1 million and $83.0 million for the three months ended March 31, 2019 and 2018 . There were no other individual countries that represented more than 10% of consolidated total revenue for the three months ended March 31, 2019 and 2018 . Revenue is attributed to individual countries based on the location of the customer. The following table summarizes gross profit by reportable segment and category for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 North America Service gross profit: Local $ 161,082 $ 166,756 Goods 2,563 3,941 Travel 15,268 16,002 Product gross profit - Goods 30,889 32,981 Total North America gross profit 209,802 219,680 International Service gross profit: Local 68,978 70,215 Goods 1,268 3,087 Travel 8,041 10,651 Product gross profit - Goods 17,927 21,252 Total International gross profit $ 96,214 $ 105,205 The following table summarizes operating income (loss) by reportable segment for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Operating income (loss) (1) : North America $ 5,336 $ (1,860 ) International (3,141 ) 5,245 Total operating income (loss) $ 2,195 $ 3,385 (1) Includes stock-based compensation of $14.8 million and $17.9 million for North America and $1.6 million and $1.4 million for International for the three months ended March 31, 2019 and 2018 . The following table summarizes total assets by reportable segment as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Total assets: North America (1) $ 918,502 $ 958,412 International (1) 587,510 683,730 Consolidated total assets $ 1,506,012 $ 1,642,142 (1) North America contains assets from the United States of $899.5 million and $940.5 million as of March 31, 2019 and December 31, 2018 . International contains assets from Ireland of $204.6 million as of December 31, 2018 . Assets from Ireland were less than 10% of consolidated total assets as of March 31, 2019 . There were no other individual countries that represented more than 10% of consolidated total assets as of March 31, 2019 and December 31, 2018 .

DESCRIPTION OF BUSINESS AND B_2

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation, Policy [Policy Text Block]	Principles of Consolidation The condensed consolidated financial statements include the accounts of Groupon, Inc. and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The condensed consolidated financial statements were prepared in accordance with U.S. GAAP and include the assets, liabilities, revenue and expenses of all wholly-owned subsidiaries and majority-owned subsidiaries over which we exercise control and a variable interest entity for which we have determined that we are the primary beneficiary. In the first quarter of 2019, we extended our arrangement through July 2022 with the strategic partner in the variable interest entity that we consolidate. Outside stockholders' interests in subsidiaries are shown on the condensed consolidated financial statements as Noncontrolling interests. Investments in entities in which we do not have a controlling financial interest are accounted for under the equity method, the fair value option, as available-for-sale securities or at cost adjusted for observable price changes and impairments, as appropriate.
New Accounting Pronouncements, Policy [Policy Text Block]	Adoption of New Accounting Standards We adopted the guidance in ASU 2016-02, Leases (Topic 842) on January 1, 2019. This ASU requires the recognition of lease assets and liabilities for operating leases, in addition to the finance lease assets and liabilities historically recorded on our condensed consolidated balance sheets. See Note 6 , Leases , for information on the impact of adopting Topic 842 on our accounting policies. We adopted the guidance in ASU 2018-07, Compensation - Stock Compensation (Topic 718) - Improvements to Nonemployee Share-Based Payment Accounting, on January 1, 2019. This ASU expands the scope to make the guidance for share-based payment awards to nonemployees consistent with the guidance for share-based payment awards to employees. The adoption of ASU 2018-07 did not have a material impact on the condensed consolidated financial statements. We adopted the guidance in ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This ASU requires entities in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40, Internal Use Software, to determine which costs to implement the service contract would be capitalized as an asset related to the service contract and which costs would be expensed. The requirements of ASU 2018-15 have been applied on a prospective basis to implementation costs incurred on or after January 1, 2019. As a result of the adoption of ASU 2018-15, we capitalized $0.9 million of implementation costs for the three months ended March 31, 2019 . Those capitalized costs are included within Other non-current assets on the condensed consolidated balance sheet as of March 31, 2019 . We have not recognized any amortization related to these implementation costs. We will amortize the implementation costs on a straight-line basis over the term of the associated hosting arrangement for each module or component of the related hosting arrangement when it is ready for its intended use. Amortization costs will be recorded in Selling, general and administrative expense on the condensed consolidated statements of operations.
Reclassification, Policy [Policy Text Block]	Reclassifications and Terminology Changes Certain reclassifications have been made to the condensed consolidated financial statements of prior periods and the accompanying notes to conform to the current period presentation
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires estimates and assumptions that affect the reported amounts and classifications of assets and liabilities, revenue and expenses, and the related disclosures of contingent liabilities in the condensed consolidated financial statements and accompanying notes. Estimates are used for, but not limited to, variable consideration from unredeemed vouchers, income taxes, initial valuation and subsequent impairment testing of goodwill and intangible assets, investments, customer refunds, contingent liabilities and the useful lives of property, equipment and software and intangible assets. Actual results could differ materially from those estimates.

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table summarizes goodwill activity by segment for the three months ended March 31, 2019 (in thousands): North America International Consolidated Balance as of December 31, 2018 $ 178,685 $ 146,806 $ 325,491 Foreign currency translation — (912 ) (912 ) Balance as of March 31, 2019 $ 178,685 $ 145,894 $ 324,579
Schedule of Intangible Assets	The following table summarizes intangible assets as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Asset Category Gross Carrying Value Accumulated Amortization Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value Customer relationships $ 16,200 $ 13,050 $ 3,150 $ 16,200 $ 11,700 $ 4,500 Merchant relationships 22,004 5,208 16,796 21,554 4,105 17,449 Trade names 9,533 6,943 2,590 9,476 6,799 2,677 Developed technology 13,810 13,527 283 13,825 13,485 340 Patents 21,112 16,844 4,268 20,508 16,451 4,057 Other intangible assets 26,109 10,537 15,572 26,007 9,629 16,378 Total $ 108,768 $ 66,109 $ 42,659 $ 107,570 $ 62,169 $ 45,401
Schedule of Estimated Future Amortization Expense	As of March 31, 2019 , estimated future amortization expense related to intangible assets is as follows (in thousands): Remaining amounts in 2019 $ 10,179 2020 7,754 2021 7,017 2022 6,701 2023 5,543 Thereafter 5,465 Total $ 42,659

INVESTMENTS (Tables)

INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Schedule of Equity Method Investments [Abstract]
Summary of Investments	The following table summarizes investments as of March 31, 2019 and December 31, 2018 (dollars in thousands): March 31, 2019 Percent Ownership of Voting Stock December 31, 2018 Percent Ownership of Voting Stock Available-for-sale securities - redeemable preferred shares $ 10,394 19% to 25% $ 10,340 19% to 25% Fair value option investments 32,494 10% to 19% 73,902 10% to 19% Other equity investments (1) 24,025 1% to 19% 24,273 1% to 19% Total investments $ 66,913 $ 108,515 (1) Represents equity investments without readily determinable fair values. We have elected to record equity investments without readily determinable fair values at cost adjusted for observable price changes and impairments. There were no adjustments for observable price changes related to these investments
Schedule of Activity for Available For Sale Securities	The following table summarizes amortized cost, gross unrealized gain, gross unrealized loss and fair value of redeemable preferred shares as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Amortized cost $ 9,961 $ 9,961 Gross unrealized gain 433 379 Gross unrealized loss — — Fair value $ 10,394 $ 10,340
Schedule of Gains and Losses due to Changes in Fair Value of Investments	The following table summarizes gains and losses due to changes in fair value of those investments for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Monster LP $ (41,459 ) $ (5,231 ) Nearbuy 51 198 Total $ (41,408 ) $ (5,033 )

SUPPLEMENTAL CONSOLIDATED BAL_2

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Schedule of Other Income (Expense)	The following table summarizes other income (expense), net for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Interest income $ 1,936 $ 1,509 Interest expense (5,691 ) (5,493 ) Changes in fair value of investments (41,408 ) (5,033 ) Foreign currency gains (losses), net (1,679 ) 1,398 Other (13 ) (896 ) Other income (expense), net $ (46,855 ) $ (8,515 )
Schedule of Prepaid and Other Current Assets	The following table summarizes prepaid expenses and other current assets as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Merchandise inventories $ 30,652 $ 33,739 Prepaid expenses 27,517 28,209 Income taxes receivable 5,495 6,717 Other 19,022 19,450 Total prepaid expenses and other current assets $ 82,686 $ 88,115
Schedule of Accrued Merchant and Supplier Payables	The following table summarizes accrued merchant and supplier payables as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Accrued merchant payables $ 361,735 $ 371,279 Accrued supplier payables (1) 150,993 280,502 Total accrued merchant and supplier payables $ 512,728 $ 651,781 (1) Amounts include payables to suppliers of inventories and providers of shipping and fulfillment services.
Schedule of Accrued Expenses and Other Current Liabilities	The following table summarizes accrued expenses and other current liabilities as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Refunds reserve $ 21,350 $ 27,957 Compensation and benefits 47,521 56,173 Accrued marketing 35,070 39,094 Customer credits 15,403 15,118 Income taxes payable 8,685 8,987 Deferred revenue 21,161 25,452 Current portion of lease obligations (1) 42,806 17,207 Other 64,064 77,046 Total accrued expenses and other current liabilities $ 256,060 $ 267,034
Schedule of Other Non-current Liabilities	The following table summarizes other non-current liabilities as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Contingent income tax liabilities $ 31,751 $ 39,858 Deferred rent (1) — 32,186 Deferred income taxes 3,880 6,619 Other 18,042 22,025 Total other non-current liabilities $ 53,673 $ 100,688 (1) Non-current operating lease liabilities as of March 31, 2019 are included within Operating lease obligations on the condensed consolidated balance sheet as a result of the adoption of Topic 842 on January 1, 2019. Refer to Note 6 , Leases , for additional information.

FINANCING ARRANGEMENTS (Tables)

FINANCING ARRANGEMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Notes	The carrying amount of the Notes consisted of the following as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Liability component: Principal amount $ 250,000 $ 250,000 Less: debt discount (45,156 ) (48,331 ) Net carrying amount of liability component $ 204,844 $ 201,669 Net carrying amount of equity component $ 67,014 $ 67,014
Schedule of Convertible Debt Interest Expense	During the three months ended March 31, 2019 and 2018 , we recognized interest costs on the Notes as follows (in thousands): Three Months Ended March 31, 2019 2018 Contractual interest (3.25% of the principal amount per annum) $ 2,032 $ 2,032 Amortization of debt discount 3,175 2,866 Total $ 5,207 $ 4,898

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lease, Cost [Table Text Block]	The following table summarizes our lease cost and sublease income for the three months ended March 31, 2019 (in thousands): Three Months Ended March 31, 2019 Financing lease cost: Amortization of right-of-use assets $ 6,756 Interest on lease liabilities 307 Total finance lease cost 7,063 Operating lease cost 8,474 Variable lease cost 892 Short-term lease cost 41 Sublease income, gross (1,312 ) Total lease cost $ 15,158 The following summarizes right-of-use assets as of March 31, 2019 (in thousands): March 31, 2019 Right-of-use assets - operating leases $ 109,555 Right-of-use assets - finance leases (1) 32,196 Total right-of-use assets, gross 141,751 Less: accumulated depreciation and amortization (13,197 ) Right-of-use assets, net $ 128,554
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	As of March 31, 2019 , the future payments under finance leases and operating leases for each of the next five years and thereafter are as follows (in thousands): Finance Leases Operating Leases Remaining in 2019 $ 11,373 $ 26,612 2020 7,654 31,932 2021 4,806 26,998 2022 715 26,114 2023 12 21,917 Thereafter — 32,600 Total minimum lease payments 24,560 166,173 Less: Amount representing interest (1,272 ) (24,964 ) Present value of net minimum lease payments 23,288 141,209 Less: Current portion of lease obligations (12,596 ) (30,210 ) Total long-term lease obligations $ 10,692 $ 110,999
Operating Lease, Lease Income [Table Text Block]	As of March 31, 2019 , the future amounts due under subleases for each of the next five years and thereafter are as follows (in thousands): Subleases Remaining in 2019 $ 3,905 2020 5,027 2021 5,065 2022 5,103 2023 4,385 Thereafter 4,891 Total future sublease income $ 28,376
Supplemental Cash Flow Information Related to Leases [Table Text Block]	The following table summarizes supplemental cash flow information on our leasing obligations for the three months ended March 31, 2019 (in thousands): Three Months Ended March 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 307 Operating cash flows from operating leases (6,481 ) Financing cash flows from finance leases (6,756 )

STOCKHOLDERS' EQUITY AND COMP_2

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS Tables (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation, Activity [Table Text Block]	The stock-based compensation expense related to stock awards issued under the Plans and acquisition-related awards are presented within the following line items of the condensed consolidated statements of operations for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Cost of revenue $ 378 $ 396 Marketing 1,425 1,794 Selling, general and administrative 14,608 17,088 Other income (expense), net — 48 Total stock-based compensation expense $ 16,411 $ 19,326 We capitalized $1.3 million and $1.7 million of stock-based compensation for the three months ended March 31, 2019 and 2018 , in connection with internally-developed software.
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]	The table below summarizes restricted stock unit activity under the Plans for the three months ended March 31, 2019 : Restricted Stock Units Weighted-Average Grant Date Fair Value (per unit) Unvested at December 31, 2018 26,623,432 $ 4.47 Granted 5,759,900 3.89 Vested (3,382,842 ) 4.43 Forfeited (2,828,751 ) 4.39 Unvested at March 31, 2019 26,171,739 4.35
Share-based Compensation, Performance and Market-Based Performance Shares Units Activity [Table Text Block]	The table below summarizes Performance Share Unit activity under the Plans for the three months ended March 31, 2019 : Performance Share Units Weighted-Average Grant Date Fair Value (per unit) Market-based Performance Share Units Weighted-Average Grant Date Fair Value (per unit) Unvested at December 31, 2018 3,431,918 $ 4.90 — $ — Granted 4,013,126 3.96 8,486,708 3.03 Vested (777,573 ) 4.88 — — Forfeited (2,191,878 ) 4.90 — — Unvested at March 31, 2019 4,475,593 4.06 8,486,708 3.03
Schedule of Share-based Compensation, Stock Options and Stock Appreciation Rights Award Activity [Table Text Block]	The table below summarizes stock option activity for the three months ended March 31, 2019 : Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) (1) Outstanding and exercisable at December 31, 2018 212,787 $ 1.80 1.37 $ 298 Exercised (12,500 ) 0.68 Outstanding and exercisable at March 31, 2019 200,287 $ 1.85 1.14 $ 340 (1) The aggregate intrinsic value of options outstanding and exercisable represents the total pretax intrinsic value (the difference between the fair value of our stock on the last day of each period and the exercise price, multiplied by the number of options where the fair value exceeds the exercise price) that would have been received by the option holders had all option holders exercised their options as of March 31, 2019 and December 31, 2018 .

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred Revenue, by Arrangement, Disclosure	The following table summarizes the activity in the liability for customer credits for the three months ended March 31, 2019 (in thousands): Customer Credits Balance as of December 31, 2018 $ 15,118 Credits issued 27,803 Credits redeemed (1) (25,020 ) Breakage revenue recognized (2,560 ) Foreign currency translation 62 Balance as of March 31, 2019 $ 15,403 (1) Customer credits can be redeemed through our online marketplaces for goods or services provided by a third-party merchant or for merchandise inventory sold by us. When customer credits are redeemed for goods or services provided by a third-party merchant, service revenue is recognized on a net basis as the difference between the carrying amount of the customer credit liability derecognized and the amount due to the merchant for the related transaction. When customer credits are redeemed for merchandise inventory sold by us, product revenue is recognized on a gross basis equal to the amount of the customer credit liability derecognized. Customer credits are typically used within one year of issuance.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables summarize assets that are measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 (in thousands): Fair Value Measurement at Reporting Date Using March 31, 2019 Quoted Prices in Active Markets for Significant Other Significant Assets: Fair value option investments $ 32,494 $ — $ — $ 32,494 Available-for-sale securities - redeemable preferred shares 10,394 — — 10,394 Liabilities: Contingent consideration 1,586 — — 1,586 Fair Value Measurement at Reporting Date Using December 31, 2018 Quoted Prices in Active Markets for Significant Other Significant Assets: Fair value option investments $ 73,902 $ — $ — $ 73,902 Available-for-sale securities - redeemable preferred shares 10,340 — — 10,340 Liabilities: Contingent consideration 1,529 — — 1,529
Fair Value, Assets and Liabilities, Reconciliation of Level 3 Inputs	The following table provides a roll-forward of the fair value of recurring Level 3 fair value measurements for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Assets Fair value option investments: Beginning Balance $ 73,902 $ 82,966 Total gains (losses) included in earnings (41,408 ) (5,033 ) Ending Balance $ 32,494 $ 77,933 Unrealized gains (losses) still held (1) $ (41,408 ) $ (5,033 ) Available-for-sale securities Convertible debt securities: Beginning Balance $ — $ 11,354 Total gains (losses) included in other comprehensive income (loss) — (501 ) Total gains (losses) included in earnings (2) — 217 Ending Balance $ — $ 11,070 Unrealized gains (losses) still held (1) $ — $ (284 ) Redeemable preferred shares: Beginning Balance $ 10,340 $ 15,431 Total gains (losses) included in other comprehensive income (loss) 54 — Impairment included in earnings — (855 ) Ending Balance $ 10,394 $ 14,576 Unrealized gains (losses) still held (1) $ 54 $ (855 ) Liabilities Contingent Consideration: Beginning Balance $ 1,529 $ — Total losses (gains) included in earnings 22 — Foreign currency translation 35 — Ending Balance $ 1,586 $ — Unrealized gains (losses) still held (1) $ 22 $ —

INCOME (LOSS) PER SHARE (Tables

INCOME (LOSS) PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Income (Loss) Per Share	The following table sets forth the computation of basic and diluted net income (loss) per share of common stock for the three months ended March 31, 2019 and 2018 (in thousands, except share and per share amounts): Three Months Ended March 31, 2019 2018 Basic and diluted net income (loss) per share: Numerator Net income (loss) - continuing operations $ (41,170 ) $ (2,795 ) Less: Net income (loss) attributable to noncontrolling interests 3,479 4,093 Net income (loss) attributable to common stockholders - continuing operations (44,649 ) (6,888 ) Net income (loss) attributable to common stockholders - discontinued operations 2,162 — Net income (loss) attributable to common stockholders $ (42,487 ) $ (6,888 ) Denominator Weighted-average common shares outstanding 570,095,128 561,735,937 Basic and diluted net income (loss) per share: Continuing operations $ (0.08 ) $ (0.01 ) Discontinued operations 0.01 0.00 Basic and diluted net income (loss) per share $ (0.07 ) $ (0.01 )
Schedule of Weighted-Average Potentially Dilutive Instruments	The following weighted-average potentially dilutive instruments are not included in the diluted net income (loss) per share calculations above because they would have had an antidilutive effect on the net income (loss) per share from continuing operations: Three Months Ended March 31, 2019 2018 Restricted stock units 27,088,851 28,033,489 Other stock-based compensation awards 1,752,744 3,212,026 Convertible senior notes 46,296,300 46,296,300 Warrants 46,296,300 46,296,300 Total 121,434,195 123,838,115

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of Revenue by Reportable Segment	The following table summarizes revenue by reportable segment and category for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 North America Service revenue: Local $ 180,377 $ 187,411 Goods 3,127 4,874 Travel 18,941 20,084 Product revenue - Goods 154,720 180,887 Total North America revenue (1) 357,165 393,256 International Service revenue: Local 73,190 74,578 Goods 1,455 3,414 Travel 8,737 11,436 Product revenue - Goods 137,863 143,856 Total International revenue (1) $ 221,245 $ 233,284 (1) North America includes revenue from the United States of $348.8 million and $385.4 million for the three months ended March 31, 2019 and 2018 . International includes revenue from the United Kingdom of $81.1 million and $83.0 million for the three months ended March 31, 2019 and 2018 . There were no other individual countries that represented more than 10% of consolidated total revenue for the three months ended March 31, 2019 and 2018 .
Schedule of Gross Profit by Reportable Segment	The following table summarizes gross profit by reportable segment and category for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 North America Service gross profit: Local $ 161,082 $ 166,756 Goods 2,563 3,941 Travel 15,268 16,002 Product gross profit - Goods 30,889 32,981 Total North America gross profit 209,802 219,680 International Service gross profit: Local 68,978 70,215 Goods 1,268 3,087 Travel 8,041 10,651 Product gross profit - Goods 17,927 21,252 Total International gross profit $ 96,214 $ 105,205
Schedule of Operating Income by Reportable Segment	The following table summarizes operating income (loss) by reportable segment for the three months ended March 31, 2019 and 2018 (in thousands): Three Months Ended March 31, 2019 2018 Operating income (loss) (1) : North America $ 5,336 $ (1,860 ) International (3,141 ) 5,245 Total operating income (loss) $ 2,195 $ 3,385 (1) Includes stock-based compensation of $14.8 million and $17.9 million for North America and $1.6 million and $1.4 million for International for the three months ended March 31, 2019 and 2018 .
Schedule of Total Assets by Segment	The following table summarizes total assets by reportable segment as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Total assets: North America (1) $ 918,502 $ 958,412 International (1) 587,510 683,730 Consolidated total assets $ 1,506,012 $ 1,642,142 (1) North America contains assets from the United States of $899.5 million and $940.5 million as of March 31, 2019 and December 31, 2018 . International contains assets from Ireland of $204.6 million as of December 31, 2018 . Assets from Ireland were less than 10% of consolidated total assets as of March 31, 2019 . There were no other individual countries that represented more than 10% of consolidated total assets as of March 31, 2019 and December 31, 2018 .

DESCRIPTION OF BUSINESS AND B_3

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019USD ($)
Item Effected [Line Items]
Number of segments	2
Accounting Standards Update 2018-15 [Member]
Item Effected [Line Items]
Capitalized implementation costs		$ 0.9

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 324,579	$ 325,491
Foreign currency translation	(912)
North America
Goodwill [Line Items]
Goodwill	178,685	178,685
Foreign currency translation	0
International
Goodwill [Line Items]
Goodwill	145,894	$ 146,806
Foreign currency translation	$ (912)

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 108,768	$ 107,570
Accumulated Amortization	66,109	62,169
Net Carrying Value	42,659	45,401
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	16,200	16,200
Accumulated Amortization	13,050	11,700
Net Carrying Value	3,150	4,500
Merchant relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	22,004	21,554
Accumulated Amortization	5,208	4,105
Net Carrying Value	16,796	17,449
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	9,533	9,476
Accumulated Amortization	6,943	6,799
Net Carrying Value	2,590	2,677
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	13,810	13,825
Accumulated Amortization	13,527	13,485
Net Carrying Value	283	340
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	21,112	20,508
Accumulated Amortization	16,844	16,451
Net Carrying Value	4,268	4,057
Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	26,109	26,007
Accumulated Amortization	10,537	9,629
Net Carrying Value	$ 15,572	$ 16,378

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Estimated Future Amortization Expense (Details) $ in Thousands	Mar. 31, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remaining amounts in 2019	$ 10,179
2020	7,754
2021	7,017
2022	6,701
2023	5,543
Thereafter	5,465
Total	$ 42,659

GOODWILL AND OTHER INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLE ASSETS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangible assets	$ 3,894	$ 2,940
Minimum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life	1 year
Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life	10 years

INVESTMENTS - Summary of Invest

INVESTMENTS - Summary of Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investments (including $42,888 and $84,242 at March 31, 2019 and December 31, 2018, at fair value)	$ 66,913	$ 108,515
Redeemable Preferred Stock
Schedule of Equity Method Investments [Line Items]
Available-for-sale securities, non-current	10,394	10,340
Fair Value Option Investments
Schedule of Equity Method Investments [Line Items]
Equity method investments	32,494	73,902
Other Equity Investments
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 24,025	$ 24,273
Minimum
Schedule of Equity Method Investments [Line Items]
Available for sale securities, percent ownership of voting stock	19.00%	19.00%
Minimum | Fair Value Option Investments
Schedule of Equity Method Investments [Line Items]
Equity method investment, percent ownership of voting stock	10.00%	10.00%
Minimum | Other Equity Investments
Schedule of Equity Method Investments [Line Items]
Equity method investment, percent ownership of voting stock	1.00%	1.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Available for sale securities, percent ownership of voting stock	25.00%	25.00%
Maximum | Fair Value Option Investments
Schedule of Equity Method Investments [Line Items]
Equity method investment, percent ownership of voting stock	19.00%	19.00%
Maximum | Other Equity Investments
Schedule of Equity Method Investments [Line Items]
Equity method investment, percent ownership of voting stock	19.00%	19.00%

INVESTMENTS - Schedule of Activ

INVESTMENTS - Schedule of Activity for Available For Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Abstract]
Available-for-sale Securities, Amortized Cost Basis	$ 9,961	$ 9,961
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	433	379
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Available-for-sale Securities	$ 10,394	$ 10,340

INVESTMENTS - Additional Inform

INVESTMENTS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Gain (loss) from changes in fair value of investments	$ 41,408	$ 5,033
Monster LP
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	27,900		$ 69,400
Gain (loss) from changes in fair value of investments	$ 41,459	5,231
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Discount Rate	26.00%		21.00%
Nearbuy
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 4,600		$ 4,500
Gain (loss) from changes in fair value of investments	$ (51)	$ (198)

SUPPLEMENTAL CONSOLIDATED BAL_3

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Other Income (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Interest income	$ 1,936	$ 1,509
Interest expense	(5,691)	(5,493)
Changes in fair value of investments	(41,408)	(5,033)
Foreign currency gains (losses), net	(1,679)	1,398
Other	(13)	(896)
Other income (expense), net	$ (46,855)	$ (8,515)

SUPPLEMENTAL CONSOLIDATED BAL_4

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Merchandise inventories	$ 30,652	$ 33,739
Prepaid expenses	27,517	28,209
Income taxes receivable	5,495	6,717
Other	19,022	19,450
Total prepaid expenses and other current assets	$ 82,686	$ 88,115

SUPPLEMENTAL CONSOLIDATED BAL_5

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Accrued Merchant and Supplier Payables (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Accrued merchant payables	$ 361,735	$ 371,279
Accrued supplier payables (1)	150,993	280,502
Total accrued merchant and supplier payables	$ 512,728	$ 651,781

SUPPLEMENTAL CONSOLIDATED BAL_6

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Accrued Expense and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Refunds reserve	$ 21,350	$ 27,957
Compensation and benefits	47,521	56,173
Accrued marketing	35,070	39,094
Customer credits	15,403	15,118
Income taxes payable	8,685	8,987
Deferred revenue	21,161	25,452
Operating Lease, Liability, Current	42,806	17,207
Finance Lease, Liability, Current	12,596
Other	64,064	77,046
Total accrued expenses and other current liabilities	$ 256,060	$ 267,034

SUPPLEMENTAL CONSOLIDATED BAL_7

SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Other Non-current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Contingent income tax liabilities	$ 31,751	$ 39,858
Deferred rent (1)	0	32,186
Deferred income taxes	3,880	6,619
Other	18,042	22,025
Total other non-current liabilities	$ 53,673	$ 100,688

FINANCING ARRANGEMENTS - Schedu

FINANCING ARRANGEMENTS - Schedule of Notes (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal amount		$ 250,000	$ 250,000
Less: debt discount		(45,156)	(48,331)
Net carrying amount of liability component		204,844	201,669
Debt Instrument, Convertible, Remaining Discount Amortization Period	3 years 6 months
Additional Paid-In Capital
Debt Instrument [Line Items]
Net carrying amount of equity component		$ 67,014	$ 67,014

FINANCING ARRANGEMENTS - Sche_2

FINANCING ARRANGEMENTS - Schedule of Convertible Debt Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Disclosure [Abstract]
Contractual interest (3.25% of the principal amount per annum)	$ 2,032	$ 2,032
Amortization of debt discount	3,175	2,866
Total	$ 5,207	$ 4,898

FINANCING ARRANGEMENTS - Conver

FINANCING ARRANGEMENTS - Convertible Senior Notes (Details)	Apr. 04, 2016USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Mar. 31, 2019USD ($)$ / shares	Mar. 31, 2018USD ($)
Debt Instrument [Line Items]
Net proceeds		$ 243,200,000
Stated interest rate	3.25%
Principal amount converted initially	$ 1,000
Number of shares converted (in shares) | shares	185.1852
Common stock, par value (in usd per share) | $ / shares				$ 6
Closing price of stock, trigger price (in usd per share)	150.00%
Number of threshold trading days	20
Consecutive trading days	30
Effective interest rate				9.75%
Debt related commitment fees and issuance costs			$ 6,800,000
Debt issuance costs			4,800,000
Equity component of convertible debt			$ 2,000,000
Estimated fair value of convertible notes				$ 274,100,000	$ 257,100,000
Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount of convertible senior notes	$ 250,000,000
Conversion price (in usd per share) | $ / shares	$ 5.40
Common stock, par value (in usd per share) | $ / shares				$ 3.55

FINANCING ARRANGEMENTS - Note H

FINANCING ARRANGEMENTS - Note Hedges and Warrants (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	May 09, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Cost of convertible note hedges		$ 59.1
Number of shares available to be purchased (in shares)	46.3
Strike price (in usd per share)	$ 5.40
Cash proceeds from issuance of warrants				$ 35.5
Incremental common shares attributable to dilutive effect			46.3
Exercise price (in usd per share)			$ 8.50

FINANCING ARRANGEMENTS - Revolv

FINANCING ARRANGEMENTS - Revolving Credit Facility (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2016	Apr. 04, 2016
Debt Instrument [Line Items]
Aggregate principal amount	$ 250
Stated interest rate				3.25%
Unrestricted cash covenant amount			$ 400
Amount of accounts held with lenders			$ 200
Outstanding amount of lines of credit	$ 17.5	$ 19.2
Minimum
Debt Instrument [Line Items]
Unused commitment fee percentage	0.25%
Maximum
Debt Instrument [Line Items]
Unused commitment fee percentage	0.40%
Letter of Credit
Debt Instrument [Line Items]
Aggregate principal amount	$ 45
Letter of Credit | Base Rate | Minimum
Debt Instrument [Line Items]
Stated interest rate	0.50%
Letter of Credit | Base Rate | Maximum
Debt Instrument [Line Items]
Stated interest rate	2.25%
Geographic Distribution, Domestic
Debt Instrument [Line Items]
Outstanding stock percentage	100.00%
Geographic Distribution, Foreign
Debt Instrument [Line Items]
Outstanding stock percentage	65.00%

LEASES - Additional Information

LEASES - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2016	Jan. 01, 2019
Operating Lease, Right-of-Use Asset	$ 109,555,000			$ 109,600,000
Lessor, Operating Lease, Payments to be Received	28,376
Sublease Income	$ 1,312,000
Finance Lease, Weighted Average Remaining Lease Term	2 years 14 days
Operating Lease, Weighted Average Remaining Lease Term	5 years 4 months 27 days
Finance Lease, Weighted Average Discount Rate, Percent	4.97%
Operating Lease, Weighted Average Discount Rate, Percent	5.80%
Uptake [Member]
Sublease Income	$ 700,000	$ 500,000	$ 18,200,000
Minimum
Leases, Discount Rate		1.50%
Maximum
Leases, Discount Rate		6.91%
Accumulated Deficit | Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 0

LEASES Right-of-Use Assets (Det

LEASES Right-of-Use Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Leases [Abstract]
Operating Lease, Right-of-Use Asset	$ 109,555	$ 109,600
Finance Lease, Right-of-Use Asset	32,196
Lease, Right of Use Asset	141,751
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(13,197)
Lease, Right of Use Asset, Net	$ 128,554

LEASES Total Lease Cost (Detail

LEASES Total Lease Cost (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 6,756
Finance Lease, Interest Expense	307
Finance Lease, Liability	7,063
Operating Lease, Cost	8,474
Operating Lease, Liability	141,209
Variable Lease, Cost	892
Short-term Lease, Cost	41
Sublease Income	(1,312)
Lease, Cost	$ 15,158

LEASES Future Lease Amount (Det

LEASES Future Lease Amount (Details) - USD ($)	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
Finance Lease, Liability, Payments, Remainder of Fiscal Year	$ 11,373,000
Finance Lease, Liability, Payments, Due Year Two	7,654,000
Finance Lease, Liability, Payments, Due Year Three	4,806,000
Finance Lease, Liability, Payments, Due Year Four	715,000
Finance Lease, Liability, Payments, Due Year Five	12,000
Finance Lease, Liability, Payments, Due after Year Five	0
Finance Lease, Liability, Payments, Due	24,560,000
Finance Lease, Liability, Undiscounted Excess Amount	(1,272,000)
Finance Lease, Liability	23,288,000
Finance Lease, Liability, Current	(12,596,000)
Finance Lease, Liability, Noncurrent	10,692,000
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	26,612,000
Lessee, Operating Lease, Liability, Payments, Due Year Two	31,932,000
Lessee, Operating Lease, Liability, Payments, Due Year Three	26,998,000
Lessee, Operating Lease, Liability, Payments, Due Year Four	26,114,000
Lessee, Operating Lease, Liability, Payments, Due Year Five	21,917,000
Lessee, Operating Lease, Liability, Payments, Due after Year Five	32,600,000
Lessee, Operating Lease, Liability, Payments, Due	166,173,000
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(24,964,000)
Operating Lease, Liability	141,209,000
Operating Lease, Liability, Current	(30,210,000)	$ (25,000,000)
Operating Lease, Liability, Noncurrent	$ 110,999,000		$ 0

LEASES Sublease (Details)

LEASES Sublease (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2016
Sublease Income	$ 1,312,000
Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year	3,905
Lessor, Operating Lease, Payments to be Received, Two Years	5,027
Lessor, Operating Lease, Payments to be Received, Three Years	5,065
Lessor, Operating Lease, Payments to be Received, Four Years	5,103
Lessor, Operating Lease, Payments to be Received, Five Years	4,385
Lessor, Operating Lease, Payments to be Received, Thereafter	4,891
Lessor, Operating Lease, Payments to be Received	28,376
Uptake [Member]
Sublease Income	$ 700,000	$ 500,000	$ 18,200,000
Maximum [Member]
Leases, Discount Rate		6.91%

LEASES Supplemental Cash Flow (

LEASES Supplemental Cash Flow (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Finance Lease, Interest Payment on Liability	$ 307,000
Operating Lease, Payments	(6,481,000)
Finance Lease, Principal Payments	$ (6,756,000)

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 09, 2017
Maximum exposure of indemnification liability	$ 13.3
Gain on Expiration of Indemnity Liability	2.2
Indemnification Liabilities	$ 3.2
Groupon Latin America [Member]
Estimated indemnification liability		$ 5.4

STOCKHOLDERS' EQUITY AND COMP_3

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	8,026,252
Stock Repurchase Program, Authorized Amount			$ 300,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%
Common Stock, Capital Shares Reserved for Future Issuance	42,997,198
Share price (in usd per share)	$ 6
Share-based Compensation Arrangement By Share-based Payment Award, Fair Value Assumptions, Cost Of Equity Rate	12.80%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,010,000,000
Employee Stock Option
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	10,000,000
Restricted Stock Units (RSUs) [Member]
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 3.89
Minimum
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Minimum | Restricted Stock Units (RSUs) [Member]
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
Maximum
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Maximum | Restricted Stock Units (RSUs) [Member]
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Common Stock
Equity, Class of Treasury Stock [Line Items]
Stock Issued During Period, Shares, Employee Stock Purchase Plans	719,297	746,773
Common Class A [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Shares	4,407,995	0
Stock Repurchased During Period, Value	$ 15,100,000	$ 0
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	275,000,000

STOCKHOLDERS' EQUITY AND COMP_4

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 129,700,000
Share-based Compensation	$ 16,411,000	$ 19,326,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 6 months
Cost of Sales [Member]
Share-based Compensation	$ 378,000	396,000
Selling and Marketing Expense [Member]
Share-based Compensation	1,425,000	1,794,000
Selling, General and Administrative Expenses [Member]
Share-based Compensation	14,608,000	17,088,000
Other Income [Member]
Share-based Compensation	$ 0	$ 48,000

STOCKHOLDERS' EQUITY AND COMP_5

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS RSU (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	0
Restricted Stock Units (RSUs) [Member]
Employee Stock Ownership Plan (ESOP), Number of Allocated Shares	26,171,739	26,623,432
Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price	$ 4.35	$ 4.47
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	5,759,900
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 3.89
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	3,382,842
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value	$ 4.43
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	2,828,751
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value	$ 4.39
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Minimum [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year

STOCKHOLDERS' EQUITY AND COMP_6

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 1,300	$ 1,700
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	200,287		212,787
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$ 1.85		$ 1.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 1 month 20 days	1 year 4 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 340		$ 298
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	12,500
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 0.68
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Minimum [Member] | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year

STOCKHOLDERS' EQUITY AND COMP_7

STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS PSU (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate	49.80%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 3.03	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	8,026,252
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	8,486,708
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 3.03
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 0
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	4,475,593	3,431,918
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 4.06	$ 4.90
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	4,013,126
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 3.96
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(777,573)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 4.88
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(2,191,878)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 4.90
Market-based Performance Share Units [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	8,486,708

REVENUE RECOGNITION - Additiona

REVENUE RECOGNITION - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Deferred revenue	$ 21,161		$ 25,452
Deferred Revenue, Revenue Recognized	25,300
Amortization of Deferred Charges	5,000	$ 7,000
Revenue from Contract with Customers, Revenue constrained and ti be recognized in future periods	13,000		13,700
Prepaid expenses and other current assets
Capitalized Contract Cost [Line Items]
Deferred Costs	2,800		2,900
Other non-current assets
Capitalized Contract Cost [Line Items]
Deferred Costs	$ 10,500		$ 11,000

REVENUE RECOGNITION - Liability

REVENUE RECOGNITION - Liability for Customer Credits Rollforward (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Movement in Customer Refundable Fees [Roll Forward]
Balance as of December 31, 2018	$ 15,118
Credits issued	27,803
Credits redeemed	(25,020)
Customer Refundable Fees, Revenue Recognized	(2,560)
Foreign currency translation	62
Balance as of March 31, 2019	$ 15,403

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	$ (3,490)	$ (2,335)
Income (loss) from continuing operations	(44,660)	$ (5,130)
Accounting Standards Update 2014-09 | Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	6,400
International
Operating Loss Carryforwards [Line Items]
Proposed income tax assessment penalties	109,000
Decrease in unrecognized benefits	$ 24,000

FAIR VALUE MEASUREMENTS - Addit

FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Apr. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Document Fiscal Year Focus	2019
Contingent consideration	$ 1,586	$ 1,529	$ 2,500

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	$ 32,494	$ 73,902		$ 77,933	$ 82,966
Available-for-sale Securities	10,394	10,340
Contingent consideration	1,586	1,529	$ 2,500
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	32,494	73,902
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	0	0
Contingent consideration	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	0	0
Contingent consideration	0	0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	32,494	73,902
Contingent consideration	1,586	1,529
Redeemable Preferred Stock | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	10,394	10,340
Redeemable Preferred Stock | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Redeemable Preferred Stock | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Redeemable Preferred Stock | Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 10,394	$ 10,340

FAIR VALUE MEASUREMENTS - Fair

FAIR VALUE MEASUREMENTS - Fair Value, Assets and Liabilities, Reconciliation of Level 3 Inputs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Document Fiscal Year Focus	2019
Fair value option investments	$ 32,494	$ 77,933	$ 73,902	$ 82,966
Gain (loss) from changes in fair value of investments	(41,408)	(5,033)
Unrealized Gains (Losses) Still Held - Assets	(41,408)	(5,033)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	1,586	0	1,529	0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	22	0
Indefinite-lived Intangible Assets, Foreign Currency Translation Gain (Loss)	35	0
Fair Value, Measurement with Unobservable Inputs, Unrealized Gain Loss	22	0
Convertible Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	0	11,070	0	11,354
Unrealized Gains (Losses) Still Held - Assets	0	(284)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	(501)
Unrealized Gain (Loss) on Securities	0	217
Redeemable Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	10,394	14,576	$ 10,340	$ 15,431
Unrealized Gains (Losses) Still Held - Assets	54	(855)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	54	0
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	$ 0	$ (855)

INCOME (LOSS) PER SHARE - Sched

INCOME (LOSS) PER SHARE - Schedule of Computation of Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator
Net income (loss) - continuing operations	$ (41,170)	$ (2,795)
Less: Net income (loss) attributable to noncontrolling interests	3,479	4,093
Net income (loss) attributable to common stockholders - continuing operations	(44,649)	(6,888)
Income (loss) from discontinued operations, net of tax	2,162	0
Net income (loss) attributable to Groupon, Inc.	$ (42,487)	$ (6,888)
Denominator
Weighted-average common shares outstanding (in shares)	570,095,128	561,735,937
Basic and diluted net income (loss) per share:
Continuing operations (in usd per share)	$ (0.08)	$ (0.01)
Discontinued operations (in usd per share)	0.01	0
Basic and diluted net income (loss) per share (in usd per share)	$ (0.07)	$ (0.01)

INCOME (LOSS) PER SHARE - Sch_2

INCOME (LOSS) PER SHARE - Schedule of Weighted-Average Potentially Dilutive Instruments (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	121,434,195	123,838,115
Performance Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issuable upon vesting of outstanding performance share units (in shares)	16,512,960	3,283,114
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	27,088,851	28,033,489
Other stock-based compensation awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,752,744	3,212,026
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	46,296,300	46,296,300
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	46,296,300	46,296,300

SEGMENT INFORMATION Schedule of

SEGMENT INFORMATION Schedule of Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Revenue by Segment [Line Items]
Total revenue	$ 578,410	$ 626,540
North America
Schedule of Revenue by Segment [Line Items]
Total revenue	357,165	393,256
International
Schedule of Revenue by Segment [Line Items]
Total revenue	221,245	233,284
Local | North America
Schedule of Revenue by Segment [Line Items]
Total revenue	180,377	187,411
Local | International
Schedule of Revenue by Segment [Line Items]
Total revenue	73,190	74,578
Goods | North America
Schedule of Revenue by Segment [Line Items]
Total revenue	3,127	4,874
Goods | International
Schedule of Revenue by Segment [Line Items]
Total revenue	1,455	3,414
Travel | North America
Schedule of Revenue by Segment [Line Items]
Total revenue	18,941	20,084
Travel | International
Schedule of Revenue by Segment [Line Items]
Total revenue	8,737	11,436
UNITED STATES
Schedule of Revenue by Segment [Line Items]
Revenues	348,800	385,400
UNITED KINGDOM
Schedule of Revenue by Segment [Line Items]
Revenues	81,100	83,000
Product
Schedule of Revenue by Segment [Line Items]
Total revenue	292,583	324,743
Product | Goods | North America
Schedule of Revenue by Segment [Line Items]
Total revenue	154,720	180,887
Product | Goods | International
Schedule of Revenue by Segment [Line Items]
Total revenue	$ 137,863	$ 143,856

SEGMENT INFORMATION Schedule _2

SEGMENT INFORMATION Schedule of Gross Profit by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Gross Profit	$ 306,016	$ 324,885
North America
Segment Reporting Information [Line Items]
Gross Profit	209,802	219,680
International
Segment Reporting Information [Line Items]
Gross Profit	96,214	105,205
Service | Local | North America
Segment Reporting Information [Line Items]
Gross Profit	161,082	166,756
Service | Local | International
Segment Reporting Information [Line Items]
Gross Profit	68,978	70,215
Service | Goods | North America
Segment Reporting Information [Line Items]
Gross Profit	2,563	3,941
Service | Goods | International
Segment Reporting Information [Line Items]
Gross Profit	1,268	3,087
Service | Travel | North America
Segment Reporting Information [Line Items]
Gross Profit	15,268	16,002
Service | Travel | International
Segment Reporting Information [Line Items]
Gross Profit	8,041	10,651
Product | Goods | North America
Segment Reporting Information [Line Items]
Gross Profit	30,889	32,981
Product | Goods | International
Segment Reporting Information [Line Items]
Gross Profit	$ 17,927	$ 21,252

SEGMENT INFORMATION Schedule _3

SEGMENT INFORMATION Schedule of Operating Income by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Operating Income (Loss) by Segment
Income (loss) from operations	$ 2,195	$ 3,385
Stock-based compensation	16,411	19,326
North America
Schedule of Operating Income (Loss) by Segment
Income (loss) from operations	5,336	(1,860)
Stock-based compensation	14,800	17,900
International
Schedule of Operating Income (Loss) by Segment
Income (loss) from operations	(3,141)	5,245
Stock-based compensation	$ 1,600	$ 1,400

SEGMENT INFORMATION Schedule _4

SEGMENT INFORMATION Schedule of Total Assets by Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,506,012	$ 1,642,142
North America
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	918,502	958,412
International
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	587,510	683,730
UNITED STATES
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 899,500	940,500
IRELAND
Segment Reporting, Asset Reconciling Item [Line Items]
Assets		$ 204,600

Uncategorized Items - grpn-2019

Label	Element	Value
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	$ 403,000
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	389,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	4,332,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	$ 1,973,000