REVENUE RECOGNITION - Impact of Topic 606 on Condensed Consolidated Financial Statements (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		$ 592,883	$ 634,466	$ 1,836,819	$ 1,970,711
Total cost of revenue		286,894	325,041	882,287	1,023,768
Gross Profit		305,989	309,425	954,532	946,943
Marketing Expense		92,717	101,456	286,051	288,456
Selling, general and administrative		160,214	214,828	676,399	677,109
Restructuring charges (credits)		35	11,503	(81)	18,818
Total operating expenses		252,966	310,638	962,369	967,234
Income (loss) from operations		53,023	(1,213)	(7,837)	(20,291)
Other income (expense), net		(4,860)	7,546	(39,832)	8,822
Income (loss) from continuing operations		48,163	6,333	(47,669)	(11,469)
Income tax expense (benefit)		988	2,531	205	11,001
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		47,175	2,940	(47,874)	(24,221)
Revenue recognized from unredeemed vouchers		1,000		1,600
Hotel reservation offering revenues		18,000		9,000
Breakage revenue		10,000		27,000
Increase related to refunds on service revenue transactions		1,000		2,000
Cumulative effect of change in accounting principle, net of tax				(88,945)
Assets		(1,403,920)		(1,403,920)			$ (1,677,505)
Deferred revenue		20,709		20,709		$ 25,800	29,539
Deferred Revenue, Revenue Recognized				(25,400)
Liabilities		1,072,280		1,072,280			1,425,660
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		331,640		331,640			251,845
International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		231,732	220,252	702,148	631,228
Gross Profit		101,941	101,517	311,433	284,238
Restructuring charges (credits)		35	4,532	(258)	6,917
Income (loss) from operations		2,019	5,782	11,543	13,520
Assets		(607,209)		(607,209)			(632,433)
North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		361,151	414,214	1,134,671	1,339,483
Gross Profit		204,048	207,908	643,099	662,705
Restructuring charges (credits)		0	6,971	177	11,901
Income (loss) from operations		51,004	(6,995)	(19,380)	(33,811)
Assets		(796,711)		(796,711)			(1,045,072)
Local
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		256,005		775,289
Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		75,946	71,574	221,949	201,257
Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		180,059	194,090	553,340	602,169
Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		6,605		23,656
Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		2,584	4,370	10,965	13,638
Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		4,021	4,323	12,691	10,139
Travel
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		26,604		87,718
Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		9,387	9,801	30,529	31,599
Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		17,217	18,300	57,189	61,082
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	[1]	594,451		1,842,609
Total cost of revenue		295,503		904,214
Gross Profit		298,948		938,395
Marketing Expense		94,516		291,557
Selling, general and administrative		159,451		673,145
Restructuring charges (credits)		35		(81)
Total operating expenses		254,002		964,621
Income (loss) from operations		44,946		(26,226)
Other income (expense), net		(4,860)		(39,832)
Income (loss) from continuing operations		40,086		(66,058)
Income tax expense (benefit)		345		(571)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		39,741		(65,487)
Assets		(1,393,084)		(1,393,084)
Liabilities		1,166,079		1,166,079
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		227,005		227,005
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	[1]	231,293		703,711
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	[1]	363,158		1,138,898
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Local
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		255,361		781,671
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		75,174		223,677
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		180,187		557,994
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		7,439		23,789
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		3,420		11,005
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		4,019		12,784
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Travel
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		27,982		86,993
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		8,884		30,324
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		19,098		56,669
Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				(88,945)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		330,651		330,651			$ 250,973
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	[1]	1,568		5,790
Total cost of revenue		8,609		21,927
Gross Profit		(7,041)		(16,137)
Marketing Expense		1,799		5,506
Selling, general and administrative		(763)		(3,254)
Restructuring charges (credits)		0		0
Total operating expenses		1,036		2,252
Income (loss) from operations		(8,077)		(18,389)
Other income (expense), net		0		0
Income (loss) from continuing operations		(8,077)		(18,389)
Income tax expense (benefit)		(643)		(776)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		(7,434)		(17,613)
Assets		(10,836)		(10,836)
Liabilities		93,799		93,799
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(104,635)		(104,635)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	[1]	(439)		1,563
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	[1]	2,007		4,227
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Local
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		(644)		6,382
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		(772)		1,728
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		128		4,654
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		834		133
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		836		40
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		(2)		93
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Travel
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		1,378		(725)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		(503)		(205)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		1,881		(520)
Accounting Standards Update 2014-09 | Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				(88,900)
Cumulative Effect on Retained Earnings, Tax				6,700
Accounting Standards Update 2014-09 | Prepaid expenses and other current assets | Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				4,007
Accounting Standards Update 2014-09 | Other non-current assets | Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				10,223
Accounting Standards Update 2014-09 | Accrued merchant and supplier payables | Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				64,970
Accounting Standards Update 2014-09 | Accrued expenses and other current liabilities | Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				13,188
Accounting Standards Update 2014-09 | Other non-current liabilities | Total Groupon, Inc. Stockholders' Equity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change in accounting principle, net of tax				(3,443)
Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		289,214	302,458	886,663	919,884
Total cost of revenue		29,792	41,858	91,167	123,209
Service | Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross Profit		71,639	67,860	209,214	189,357
Service | Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross Profit		159,379	162,914	491,420	511,865
Service | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross Profit		2,320	3,639	9,972	11,800
Service | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross Profit		3,634	3,205	10,565	7,719
Service | Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross Profit		8,649	8,922	28,219	28,954
Service | Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross Profit		13,801	14,060	46,106	46,980
Service | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		290,782		892,453
Total cost of revenue		38,401		113,094
Service | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		1,568		5,790
Total cost of revenue		8,609		21,927
Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		303,669	332,008	950,156	1,050,827
Total cost of revenue		257,102	283,183	791,120	900,559
Product | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		303,669		950,156
Product | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		143,815	134,507	438,705	384,734
Gross Profit		19,333	21,096	64,028	54,127
Product | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		159,854	197,501	511,451	666,093
Gross Profit		27,234	$ 27,729	95,008	$ 96,141
Product | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		303,669		950,156
Total cost of revenue		257,102		791,120
Product | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		303,669		950,156
Product | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		143,815		438,705
Product | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		159,854		511,451
Product | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		0		0
Total cost of revenue		0		0
Product | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		0		0
Product | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		0		0
Product | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		0		$ 0
Foreign Tax Authority [Member] | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Income tax expense (benefit)		$ 6,400

[1] (1)North America includes revenue from the United States of $352.3 million and $410.5 million for the three months ended September 30, 2018 and 2017, respectively, and $1,108.8 million and $1,317.9 million for the nine months ended September 30, 2018 and 2017, respectively. International includes revenue from the United Kingdom of $94.0 million and $82.2 million for the three months ended September 30, 2018 and 2017, respectively, and $268.5 million and $222.1 million for the nine months ended September 30, 2018 and 2017, respectively. There were no other individual countries that represented more than 10% of consolidated total revenue for the three and nine months ended September 30, 2018 and 2017.