Net proceeds from the Convertible Notes used to pay for the cost of the Convertible Note Hedge

No definition available.

Name:	tree_NetproceedsfromtheConvertibleNotesusedtopayforthecostoftheConvertibleNoteHedge
Namespace Prefix:	tree_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of Shares Covered by the Hedge Transactions

+ References

No definition available.

+ Details

Name:	tree_NumberofSharesCoveredbytheHedgeTransactions
Namespace Prefix:	tree_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Premium of warrant strike price over sales price of common stock

+ References

No definition available.

+ Details

Name:	tree_Premiumofwarrantstrikepriceoversalespriceofcommonstock
Namespace Prefix:	tree_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Proceeds from Hedge and Warrants

+ References

No definition available.

+ Details

Name:	tree_ProceedsfromHedgeandWarrants
Namespace Prefix:	tree_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow for a financial contract that meets the hedge criteria as either cash flow hedge, fair value hedge or hedge of net investment in foreign operations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 27
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3581-108585

+ Details

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

- Definition

The aggregate amount paid by the entity to reacquire the right to purchase equity shares at a predetermined price, usually issued together with corporate debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

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

- Definition

The cash inflow from a financial contract that meets the hedge criteria as either cash flow hedge, fair value hedge or hedge of net investment in foreign operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 27
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3581-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Definition

The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tree_A2020WarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tree_A2017WarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DEBT (Details - Convertible Note Hedge and Warrant Transactions) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions			9 Months Ended
	Jul. 24, 2020	May 31, 2017	Sep. 30, 2020	Sep. 30, 2019	Jul. 21, 2020	May 24, 2017
Debt Instrument [Line Items]
Payment of convertible note hedge transactions			$ 124,200	$ 0
Share price			$ 306.89
Proceeds from the sale of warrants related to the Convertible Senior Notes			$ 61,180	0
Termination of convertible note hedge on the 0.625% Convertible Senior Notes			109,881	0
Payments for Repurchase of Warrants			$ 94,292	$ 0
2020 Hedge and Warrants [Member]
Debt Instrument [Line Items]
Net proceeds from the Convertible Notes used to pay for the cost of the Convertible Note Hedge	$ 63,000
Payment of convertible note hedge transactions	$ 124,200
Number of shares covered by the hedge transactions	1.2
Initial conversion price per share	$ 461.19
Strike price of warrants sold	$ 709.52
Share price					$ 354.76
Proceeds from the sale of warrants related to the Convertible Senior Notes	$ 61,200
Premium of warrant strike price over sales price of common stock	100.00%
2017 Hedge and Warrants [Member]
Debt Instrument [Line Items]
Net proceeds from the Convertible Notes used to pay for the cost of the Convertible Note Hedge		$ 18,100
Payment of convertible note hedge transactions		$ 61,500
Number of shares covered by the hedge transactions	0.8	1.4
Initial conversion price per share		$ 207.63
Strike price of warrants sold		$ 266.39
Share price						$ 156.70
Proceeds from the sale of warrants related to the Convertible Senior Notes		$ 43,400
Proceeds from Hedge and Warrants	$ 15,600
Premium of warrant strike price over sales price of common stock		70.00%