BUSINESS ACQUISITIONS - Additional information (Details)						3 Months Ended		6 Months Ended	12 Months Ended
	Sep. 30, 2019 segment	Jan. 10, 2019 USD ($)	Oct. 31, 2018 USD ($) segment payment	Jul. 23, 2018 USD ($)	Jun. 11, 2018 USD ($) payment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Contingent consideration payment, financing									$ 4,755,000	$ 21,275,000	$ 27,588,000
Contingent consideration payment, total									25,787,000	12,500,000	21,912,000
Goodwill						$ 420,139,000	$ 420,139,000		$ 420,139,000	420,139,000	348,347,000
Number of reportable segments | segment	1		1						3
Acquisition related costs										600,000	6,900,000
Change in fair value of contingent consideration									$ 5,327,000	28,402,000	10,788,000
Contingent consideration arrangements, after tax contingent consideration expense										21,500,000	7,200,000
Current contingent consideration						0	9,028,000		0	9,028,000
SnapCap
Business Acquisition [Line Items]
Contingent consideration payment, financing									3,300,000	3,000,000.0
Contingent consideration payment, total									6,000,000.0
Contingent consideration payment, operating									2,700,000
Acquisition purchase consideration									0	0	10,000
Change in fair value of contingent consideration									77,000	2,220,000	(330,000)
DepositAccounts
Business Acquisition [Line Items]
Contingent consideration payment, financing											4,000,000.0
Contingent consideration payment, total									0
Contingent consideration payment, operating										3,000,000.0
Change in fair value of contingent consideration									0	(947,000)	1,979,000
ValuePenguin
Business Acquisition [Line Items]
Acquisition purchase consideration		$ 106,100,000
Total purchase price		106,232,000
Working capital adjustment		100,000
Goodwill		71,739,000
Revenue of acquirees since acquisition date										19,800,000
Earnings of acquiree since acquisition date								$ 3,100,000
Acquisition related costs										100,000
QuoteWizard
Business Acquisition [Line Items]
Contingent consideration payment, financing							13,900,000
Contingent consideration payment, total							23,400,000
Contingent consideration payment, operating						20,200,000	9,500,000
Acquisition purchase consideration			$ 299,900,000
Total purchase price			313,355,000
Working capital adjustment			400,000
Goodwill			182,896,000
Acquisition related costs											4,800,000	$ 5,900,000
Cash on hand			$ 174,900,000
Number of payments | payment			3
Contingent consideration on acquisition date			$ 13,900,000			8,200,000			8,200,000
Change in fair value of contingent consideration									3,980,000	27,103,000	6,833,000
Contingent consideration arrangements, after tax contingent consideration expense											4,900,000
Student Loan Hero
Business Acquisition [Line Items]
Acquisition purchase consideration				$ 60,700,000
Total purchase price				60,418,000
Working capital adjustment				2,000,000.0
Goodwill				40,856,000
Acquisition related costs											500,000
Severance costs				$ 2,300,000
Ovation
Business Acquisition [Line Items]
Contingent consideration payment, financing						1,400,000	$ 4,400,000
Contingent consideration payment, total						4,400,000
Contingent consideration payment, operating						$ 3,000,000.0
Acquisition purchase consideration					$ 12,200,000
Total purchase price					17,871,000
Working capital adjustment					100,000
Goodwill					$ 11,280,000
Acquisition related costs											400,000
Number of payments | payment					2
Contingent consideration on acquisition date					$ 5,800,000
Change in fair value of contingent consideration									$ 1,270,000	$ 26,000	$ 1,654,000
Earnout Payment | QuoteWizard
Business Acquisition [Line Items]
Contingent consideration range, minimum			0
Contingent consideration range, maximum			23,400,000
Earnout Payment | Ovation
Business Acquisition [Line Items]
Contingent consideration range, minimum					0
Contingent consideration range, maximum					$ 4,400,000
Revolving Credit Facility | ValuePenguin
Business Acquisition [Line Items]
Proceeds from revolving credit facility		$ 90,000,000.0
Revolving Credit Facility | QuoteWizard
Business Acquisition [Line Items]
Proceeds from revolving credit facility			$ 125,000,000.0