STOCK-BASED COMPENSATION - Summary of RSA & RSU (Details)	9 Months Ended
Sep. 30, 2021 $ / shares shares
Restricted Stock Units (RSUs)
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Number of Shares
Nonvested at the beginning of the period (in shares)	194,686
Granted (in shares)	230,785
Vested (in shares)	(79,325)
Forfeited (in shares)	(45,848)
Nonvested at the end of the period (in shares)	300,298
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share) \| $ / shares	$ 289.82
Granted (in dollars per share) \| $ / shares	221.59
Vested (in dollars per share) \| $ / shares	299.60
Forfeited (in dollars per share) \| $ / shares	266.99
Nonvested at the end of the period (in dollars per share) \| $ / shares	$ 238.28
Restricted Stock Units with performance conditions
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Number of Shares
Nonvested at the beginning of the period (in shares)	6,328
Granted (in shares)	0
Vested (in shares)	0
Forfeited (in shares)	0
Nonvested at the end of the period (in shares)	6,328
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share) \| $ / shares	$ 223.90
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	0
Forfeited (in dollars per share) \| $ / shares	0
Nonvested at the end of the period (in dollars per share) \| $ / shares	$ 223.90
Restricted Stock with performance conditions
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Number of Shares
Nonvested at the beginning of the period (in shares)	23,804
Granted (in shares)	0
Vested (in shares)	(17,853)
Forfeited (in shares)	0
Nonvested at the end of the period (in shares)	5,951
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share) \| $ / shares	$ 340.25
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	340.25
Forfeited (in dollars per share) \| $ / shares	0
Nonvested at the end of the period (in dollars per share) \| $ / shares	$ 340.25
Restricted Stock with market conditions
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Number of Shares
Nonvested at the beginning of the period (in shares)	26,674
Granted (in shares)	0
Vested (in shares)	0
Forfeited (in shares)	0
Nonvested at the end of the period (in shares)	26,674
Nonvested RSUs, Restricted Stock and Restricted Stock Units with Performance Conditions, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share) \| $ / shares	$ 340.25
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	0
Forfeited (in dollars per share) \| $ / shares	0
Nonvested at the end of the period (in dollars per share) \| $ / shares	$ 340.25
Maximum number of shared to be earned	44,545
Percentage of target number of shares	167.00%
Performance awards earned (in shares)	29,601

Performance Awards Earned

No definition available.

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

- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Maximum Shares To Be Earned

+ References

No definition available.

+ Details

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

- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Percentage Of Target Number Of Shares

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=tree_PerformanceBasedRestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=tree_MarketBasedRestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: