REVENUE RECOGNITION - Impact of Topic 606 on Condensed Consolidated Financial Statements (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		$ 295,652	[1]	$ 315,854	$ 597,449	[1]	$ 617,426
Sales Revenue, Goods, Net		321,744		346,765	646,487		718,819
Revenue, Net		617,396	[2]	662,619	1,243,936	[2]	1,336,245
Cost of Services		30,230	[3]	38,478	61,375	[3]	81,351
Cost of Goods Sold		263,508		296,074	534,018		617,376
Cost of Revenue		293,738	[3]	334,552	595,393	[3]	698,727
Gross Profit		323,658		328,067	648,543		637,518
Marketing Expense		94,178	[4]	100,658	193,334	[4]	187,000
Selling, general and administrative		294,124	[5]	230,223	516,185	[5]	462,281
Restructuring charges (credits)		(399)		4,584	(116)		7,315
Operating Expenses		387,903		335,465	709,403		656,596
Operating Income (Loss)	[6],[7]	(64,245)		(7,398)	(60,860)		(19,078)
Other Nonoperating Income (Expense)		(26,457)		5,878	(34,972)		1,276
Income (loss) from continuing operations		(90,702)		(1,520)	(95,832)		(17,802)
Income Tax Expense (Benefit)		1,552		3,883	(783)		8,470
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		(92,254)		(6,779)	(95,049)		(27,161)
Revenue recognized from unredeemed vouchers		2,900			8,500
Hotel reservation offering revenues		500			2,800
Breakage revenue		800			1,500
Increase related to refunds on service revenue transactions		9,200			17,000
Cumulative effect of change in accounting principle, net of tax					88,945
Assets	[8]	(1,488,700)			(1,488,700)			$ (1,677,505)
Deferred Revenue		21,802			21,802			25,763
Deferred Revenue, Additions		21,802
Deferred Revenue, Revenue Recognized		(25,364)
Foreign Currency Translation, Deferred Revenue		(399)
Liabilities		1,217,563			1,217,563			1,425,660
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		271,137			271,137			251,845
International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Net	[2]	237,132		210,707	470,416		410,976
Gross Profit		104,287		94,207	209,492		182,721
Restructuring charges (credits)		(576)		1,609	(293)		2,385
Operating Income (Loss)	[6],[7]	4,279		4,635	9,524		7,738
Assets	[8]	(617,478)			(617,478)			(632,433)
North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Net	[2]	380,264		451,912	773,520		925,269
Gross Profit		219,371		233,860	439,051		454,797
Restructuring charges (credits)		177		2,975	177		4,930
Operating Income (Loss)	[6],[7]	(68,524)		(12,033)	(70,384)		(26,816)
Assets	[8]	(871,222)			(871,222)			(1,045,072)
Local
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		257,295			519,284
Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		71,425		66,108	146,003		129,683
Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		185,870		207,534	373,281		408,079
Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		8,763			17,051
Sales Revenue, Goods, Net		321,744			646,487
Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		4,967		4,984	8,381		9,268
Sales Revenue, Goods, Net		151,034		128,819	294,890		250,227
Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		3,796		4,112	8,670		5,816
Sales Revenue, Goods, Net		170,710		217,946	351,597		468,592
Travel
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		29,594			61,114
Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		9,706		10,796	21,142		21,798
Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		19,888		$ 22,320	39,972		$ 42,782
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		301,653			601,671
Sales Revenue, Goods, Net		321,744			646,487
Revenue, Net	[2]	623,397			1,248,158
Cost of Services		37,273			74,693
Cost of Goods Sold		263,508			534,018
Cost of Revenue		300,781			608,711
Gross Profit		322,616			639,447
Marketing Expense		96,312			197,041
Selling, general and administrative		292,897			513,694
Restructuring charges (credits)		(399)			(116)
Operating Expenses		388,810			710,619
Operating Income (Loss)		(66,194)			(71,172)
Other Nonoperating Income (Expense)		(26,457)			(34,972)
Income (loss) from continuing operations		(92,651)			(106,144)
Income Tax Expense (Benefit)		2,438			(916)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		(95,089)			(105,228)
Assets		(1,477,062)			(1,477,062)
Liabilities		1,303,687			1,303,687
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		173,375			173,375
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Net	[2]	241,447			472,418
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Net	[2]	381,950			775,740
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Local
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		262,154			526,310
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		75,371			148,503
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		186,783			377,807
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		8,301			16,350
Sales Revenue, Goods, Net		321,744			646,487
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		4,410			7,585
Sales Revenue, Goods, Net		151,034			294,890
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		3,891			8,765
Sales Revenue, Goods, Net		170,710			351,597
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Travel
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		31,198			59,011
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		10,632			21,440
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		20,566			37,571
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		6,001			4,222
Sales Revenue, Goods, Net		0			0
Revenue, Net	[2]	6,001			4,222
Cost of Services		7,043			13,318
Cost of Goods Sold		0			0
Cost of Revenue		7,043			13,318
Gross Profit		(1,042)			(9,096)
Marketing Expense		2,134			3,707
Selling, general and administrative		(1,227)			(2,491)
Restructuring charges (credits)		0			0
Operating Expenses		907			1,216
Operating Income (Loss)		(1,949)			(10,312)
Other Nonoperating Income (Expense)		0			0
Income (loss) from continuing operations		(1,949)			(10,312)
Income Tax Expense (Benefit)		886			(133)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		(2,835)			(10,179)
Assets		(11,638)			(11,638)
Liabilities		86,124			86,124
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(97,762)			(97,762)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Net	[2]	4,315			2,002
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Net	[2]	1,686			2,220
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Local
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		4,859			7,026
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Local | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		3,946			2,500
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Local | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		913			4,526
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		(462)			(701)
Sales Revenue, Goods, Net		0			0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		(557)			(796)
Sales Revenue, Goods, Net		0			0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Goods | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		95			95
Sales Revenue, Goods, Net		0			0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Travel
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		1,604			(2,103)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Travel | International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		926			298
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Travel | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales Revenue, Services, Net		678			(2,401)
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		270,332			270,332			$ 250,973
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Income Tax Expense (Benefit)		$ 6,400			6,400
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					(88,945)
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

[1] (1)For the three months ended June 30, 2018, reflects a $9.2 million increase for refunds on service revenue transactions for which the merchant's share is not recoverable and customer credits issued for relationship purposes, which are classified as reductions of revenue under Topic 606, and an increase of $0.5 million related to the timing of recognition of revenue from hotel reservation offerings, partially offset by decreases of $2.9 million related to the timing of recognition of variable consideration from unredeemed vouchers and $0.8 million related to the timing of recognition of breakage revenue from customer credits that are not expected to be used.

[2] (1)North America includes revenue from the United States of $371.1 million and $442.7 million for the three months ended June 30, 2018 and 2017, respectively, and $756.5 million and $907.4 million for the six months ended June 30, 2018 and 2017, respectively. International includes revenue from the United Kingdom of $91.5 million and $74.4 million for the three months ended June 30, 2018 and 2017, respectively, and $174.5 million and $139.9 million for the six months ended June 30, 2018 and 2017, respectively. There were no other individual countries that represented more than 10% of consolidated total revenue for the three and six months ended June 30, 2018 and 2017.

[3] Reflects an increase for refunds on service revenue transactions for which the merchant's share is not recoverable, which are classified as a reduction of revenue under Topic 606.

[4] Reflects an increase for customer credits issued for relationship purposes, which are classified as a reduction of revenue under Topic 606.

[5] Reflects the amortization of deferred contract acquisition costs in excess of amounts capitalized in the current period.

[6] (1)Includes stock-based compensation of $15.0 million and $20.0 million for North America and $1.3 million and $1.3 million for International for the three months ended June 30, 2018 and 2017, respectively, and

[7] Includes restructuring charges (credits) of $0.2 million and $3.0 million for North America and $(0.6) million and $1.6 million for International for the three months ended June 30, 2018 and 2017, respectively

[8] (1)North America contains assets from the United States of $846.3 million and $1,006.2 million as of June 30, 2018 and December 31, 2017, respectively. International contains assets from Ireland of $162.7 million and $219.7 million as of June 30, 2018 and December 31, 2017, respectively. There were no other individual countries that represented more than 10% of consolidated total assets as of June 30, 2018 and December 31, 2017.