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ACQUISITIONS (Narrative) (Details) - USD ($)			12 Months Ended
	Oct. 22, 2019	Feb. 21, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill			$ 1,882,020,000	$ 1,611,535,000	$ 1,283,457,000
Goodwill, expected tax deductible amount			$ 166,000,000
Trade name
Business Acquisition [Line Items]
Weighted-average amortization period			12 years
STR Inc and STR Global Ltd
Business Acquisition [Line Items]
Aggregate purchase price	$ 435,000,000
Goodwill	261,436,000
Transaction costs	2,000,000
Employee retention bonus	$ 15,000,000
Period for retention payments	1 year
STR Inc and STR Global Ltd | North America
Business Acquisition [Line Items]
Goodwill	$ 159,000,000
STR Inc and STR Global Ltd | International
Business Acquisition [Line Items]
Goodwill	$ 102,000,000
ForRent, Division Of DE Holdings, Inc.
Business Acquisition [Line Items]
Aggregate purchase price		$ 376,000,000
Goodwill		266,595,000
Transaction costs		3,000,000
Employee retention bonus		12,000,000
Cash payment		$ 340,000,000
Investment owned (shares)		103,280
Purchase price, shares issued		$ 36,000,000
Goodwill, expected tax deductible amount		8,000,000
Indemnification asset		6,260,000
State uncertain income tax position liability		2,047,000
Sales taxes		5,000,000
Reversed tax liabilities due to time lapse			$ 900,000	500,000
Uncertain income tax position liability and related indemnification asset recognized as of the acquisition			$ 600,000	$ 900,000
ForRent, Division Of DE Holdings, Inc. | Maximum
Business Acquisition [Line Items]
State uncertain income tax position liability		2,000,000
ForRent, Division Of DE Holdings, Inc. | North America
Business Acquisition [Line Items]
Goodwill		$ 267,000,000
ForRent, Division Of DE Holdings, Inc. | Customer base
Business Acquisition [Line Items]
Weighted-average amortization period		10 years
ForRent, Division Of DE Holdings, Inc. | Database Rights
Business Acquisition [Line Items]
Weighted-average amortization period		3 years
ForRent, Division Of DE Holdings, Inc. | Trade name
Business Acquisition [Line Items]
Weighted-average amortization period		10 years
ForRent, Division Of DE Holdings, Inc. | Building Photography
Business Acquisition [Line Items]
Weighted-average amortization period		1 year

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