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DISCONTINUED OPERATIONS - Narrative (Details) $ in Thousands					1 Months Ended						3 Months Ended				12 Months Ended
	Jun. 17, 2020 USD ($)	Jun. 11, 2020 USD ($)	Dec. 04, 2019 USD ($)	Jun. 21, 2019 USD ($)	Apr. 30, 2021 USD ($)	Jul. 31, 2020 USD ($)	Dec. 31, 2018 USD ($) loan	Feb. 29, 2016 defendant	Jan. 31, 2016 USD ($)	Dec. 31, 2013 USD ($) claim network_lender	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2018 USD ($) loan	Dec. 31, 2019 USD ($)	Mar. 31, 2021 USD ($)	Jul. 24, 2020	Jul. 21, 2019 USD ($)	May 31, 2017	Jun. 06, 2012 USD ($)
Loan Loss Obligations
Assets											$ 1,188,990					$ 1,243,177
Annual interest rate on convertible senior notes																	0.50%		0.625%
Home Loan Center, Inc.
Loan Loss Obligations
Assets																		$ 11,200
Cash																		$ 5,900
Dividends									$ 40,000
Discover Bank \| Lending Tree Loans
Loan Loss Obligations
Asset purchase agreement proceeds from sale																				$ 55,900
Residential Funding Co. v Home Loan Center
Loan Loss Obligations
Damages sought										$ 61,000
Residential Funding Co. v Home Loan Center \| Pending litigation or appeal
Loan Loss Obligations
Number of loan originators \| network_lender										80
Number of pending claims \| claim										2
Residential Funding Co. v Home Loan Center \| Judicial Ruling
Loan Loss Obligations
Settlement offer				$ 68,500
Residential Funding Co. v Home Loan Center \| Judicial Ruling \| Damages
Loan Loss Obligations
Settlement offer				28,700										$ 28,700
Residential Funding Co. v Home Loan Center \| Judicial Ruling \| Pre-Verdict Interest
Loan Loss Obligations
Settlement offer				14,100
Residential Funding Co. v Home Loan Center \| Judicial Ruling \| Attorney Fees
Loan Loss Obligations
Settlement offer				23,100
Residential Funding Co. v Home Loan Center \| Judicial Ruling \| Pre-Judgment Interest
Loan Loss Obligations
Settlement offer				$ 2,600
Residential Funding Co. v Home Loan Center \| Settled \| ResCap \| Damages
Loan Loss Obligations
Settlement offer	$ 58,500
Loss contingency settlement payment											$ 6,400	$ 26,500
Loss contingency, receivable																$ 8,600
Lehman Brothers Holdings, Inc. Demand Letter
Loan Loss Obligations
Damages sought			$ 44,700				$ 40,200
Number of loans sold with losses \| loan							370							370
Lehman Brothers Holdings, Inc. Demand Letter \| Subsequent Event
Loan Loss Obligations
Settlement offer					$ 800
Lehman Brothers Holdings, Inc. Demand Letter \| Pending litigation or appeal
Loan Loss Obligations
Number of defendants \| defendant								149
Lehman Brothers Holdings Inc. v. LendingTree, LLC
Loan Loss Obligations
Damages sought		$ 13,300
Discontinued Operations, Disposed of by Means Other than Sale \| Home Loan Center, Inc.
Loan Loss Obligations
Loss recognized															$ 5,500
Net gain on disposal															4,500
Recognition of liability															$ 10,000
Discontinued Operations, Disposed of by Means Other than Sale \| Obligation to Repurchase Receivables Sold \| Lending Tree Loans
Loan Loss Obligations
Loss contingency settlement payment						$ 36,000
Discontinued Operations, Disposed of by Means Other than Sale \| Pending litigation or appeal \| Obligation to Repurchase Receivables Sold \| Lending Tree Loans \| Discontinued Operations
Loan Loss Obligations
Settlement offer													$ 36,000