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GOODWILL (Narrative) (Details) £ in Millions					12 Months Ended
	Jun. 12, 2019 USD ($)	Nov. 08, 2018 USD ($)	Oct. 12, 2018 GBP (£)	Oct. 12, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Feb. 21, 2018 USD ($)
Goodwill [Line Items]
Goodwill					$ 1,882,020,000	$ 1,611,535,000	$ 1,283,457,000
Acquisitions of realla					267,804,000	329,938,000
Goodwill, expected tax deductible amount					166,000,000
Goodwill, impairment					0	$ 0	$ 0
Off Campus Partners
Goodwill [Line Items]
Acquisitions of realla	$ 8,000,000
Cozy Services Ltd
Goodwill [Line Items]
Acquisitions of realla		$ 52,000,000
Acquisition of cozy		$ 53,000,000
Initial amount of cozy goodwill recognized					$ (1,000,000)
Realla Ltd
Goodwill [Line Items]
Acquisitions of realla			£ 8	$ 10,000,000
ForRent, Division Of DE Holdings, Inc.
Goodwill [Line Items]
Goodwill								$ 266,595,000
Goodwill, expected tax deductible amount								$ 8,000,000

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