GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Goodwill [Line Items]
Goodwill impairment	$ 211,973		$ 0	$ 3,318
Goodwill	3,042,139	$ 2,854,462		2,854,462	$ 2,726,859
Carrying amount of goodwill for which excess of fair value over carrying value is less than 10%	$ 709,400
Discount Rate | Maximum | Trade names
Goodwill [Line Items]
Measurement input (as a percent)	0.150
Discount Rate | Minimum | Trade names
Goodwill [Line Items]
Measurement input (as a percent)	0.105
Royalty Rate | Maximum | Trade names
Goodwill [Line Items]
Measurement input (as a percent)	0.060
Royalty Rate | Minimum | Trade names
Goodwill [Line Items]
Measurement input (as a percent)	0.010
Match Group
Goodwill [Line Items]
Impairment of indefinite-lived intangible assets	$ 4,600
Publishing
Goodwill [Line Items]
Accumulated impairment on goodwill	399,700	399,700		399,700
Applications
Goodwill [Line Items]
Goodwill impairment	211,973			0
Goodwill	292,641	504,748		504,748	504,892
Accumulated impairment on goodwill	741,100	529,100		529,100
Emerging & Other
Goodwill [Line Items]
Goodwill impairment				3,318
Goodwill	425,246	8,449		8,449	7,002
Dotdash
Goodwill [Line Items]
Accumulated impairment on goodwill	198,300	198,300		198,300
Desktop | Applications
Goodwill [Line Items]
Goodwill impairment	211,973			0
Impairment of indefinite-lived intangible assets	21,400
Goodwill	$ 53,173	265,146		265,146	265,146
Desktop | Applications | Discount Rate
Goodwill [Line Items]
Measurement input (as a percent)	0.150
Mosaic Group | Applications
Goodwill [Line Items]
Goodwill impairment	$ 0			0
Goodwill	239,468	239,602		239,602	$ 239,746
College Humor Media | Emerging & Other
Goodwill [Line Items]
Goodwill impairment	0	3,300
Accumulated impairment on goodwill	$ 14,900	$ 14,900		$ 14,900