REVENUE RECOGNITION - Liability for Customer Credits Rollforward (Details) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Movement in Customer Refundable Fees [Roll Forward]
Balance as of January 1, 2018	$ 19,414
Credits issued	97,586
Credits redeemed	(83,818)
Breakage revenue recognized	(15,639)
Foreign currency translation	(123)
Balance as of September 30, 2018	$ 17,420

Customer Refundable Fees, Foreign Currency Translation Adjustment

No definition available.

Name:	grpn_CustomerRefundableFeesForeignCurrencyTranslationAdjustment
Namespace Prefix:	grpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of proceeds that had been received in revenue related transactions that are refundable to the customers and do not meet the criteria for revenue recognition (for example, refundable membership fees).

+ References

No definition available.

+ Details

Name:	us-gaap_CustomerRefundableFees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash inflow from customers for revenue related transactions that are refundable to the customers and do not meet the criteria for revenue recognition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585

+ Details

Name:	us-gaap_CustomerRefundableFeesProceeds
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash outflow to customers for refund payments.

+ References

No definition available.

+ Details

Name:	us-gaap_CustomerRefundableFeesRefundPayments1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized attributable to customer refundable fees.

+ References

No definition available.

+ Details

Name:	us-gaap_CustomerRefundableFeesRevenueRecognized1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_MovementInCustomerRefundableFeesRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration