ACQUISITIONS (ForRent Narrative) (Details) - USD ($)		12 Months Ended
	Feb. 21, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 01, 2015
Business Acquisition [Line Items]
Goodwill		$ 1,611,535,000	$ 1,283,457,000	$ 1,254,866,000
Goodwill, expected tax deductible amount		16,000,000
ForRent, Division Of DE Holdings, Inc. [Member]
Business Acquisition [Line Items]
Aggregate purchase price	$ 376,000,000
Cash payment	$ 340,000,000
Investment owned (shares)	103,280
Purchase price, shares issued	$ 36,000,000
Goodwill	266,595,000				$ 267,000,000
Goodwill, expected tax deductible amount		$ 8,000,000
Indemnification asset	6,260,000
State uncertain income tax position liability	2,047,000
Indemnification asset	5,443,000
Indemnification asset	1,000,000
Transaction costs	3,000,000
Customer Relationships [Member] | ForRent, Division Of DE Holdings, Inc. [Member]
Business Acquisition [Line Items]
Weighted-average amortization period		10 years
Acquired Database Technology [Member] | ForRent, Division Of DE Holdings, Inc. [Member]
Business Acquisition [Line Items]
Weighted-average amortization period		3 years
Acquired trade names and other intangible assets [Member]
Business Acquisition [Line Items]
Weighted-average amortization period		12 years
Acquired trade names and other intangible assets [Member] | ForRent, Division Of DE Holdings, Inc. [Member]
Business Acquisition [Line Items]
Weighted-average amortization period		10 years
Building Photography [Member]
Business Acquisition [Line Items]
Weighted-average amortization period		2 years
Building Photography [Member] | ForRent, Division Of DE Holdings, Inc. [Member]
Business Acquisition [Line Items]
Weighted-average amortization period		1 year
Maximum [Member] | ForRent, Division Of DE Holdings, Inc. [Member]
Business Acquisition [Line Items]
State uncertain income tax position liability	2,000,000
Employee retention bonus	$ 11,627,000