REAL ESTATE AND ACQUIRED IN PLACE LEASE VALUE - Schedule of Acquisitions (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($) property
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 76.1	$ 87.4
Building	193.9	263.5
Acquired in place lease values	43.5	3.3
Investment debt	214.8	207.1
KWH Shareholders' Equity	98.7	147.1
Multifamily and Commercial [Member] \| Western United States [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	39.9
Building	123.0
Acquired in place lease values	37.2
Investment debt	112.2
KWH Shareholders' Equity	$ 87.9
Multifamily and Commercial [Member] \| Western United States [Member] \| Multifamily [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Multifamily and Commercial [Member] \| Western United States [Member] \| Commercial [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Commercial And Industrial Properties [Member] \| United Kingdom [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 29.0
Building	39.2
Acquired in place lease values	2.9
Investment debt	58.6
KWH Shareholders' Equity	$ 12.5
Commercial And Industrial Properties [Member] \| United Kingdom [Member] \| Industrial Property [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Commercial And Industrial Properties [Member] \| United Kingdom [Member] \| Residential Real Estate [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Commercial Property Acquired [Member] \| Ireland [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 7.2
Building	31.7
Acquired in place lease values	3.4
Investment debt	44.0
KWH Shareholders' Equity	$ (1.7)
Commercial Property Acquired [Member] \| Ireland [Member] \| Commercial [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Multifamily, Land Development and Commercial Properties [Member] \| Western United States [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land		72.1
Building		167.5
Acquired in place lease values		1.2
Investment debt		145.8
KWH Shareholders' Equity		$ 95.0
Multifamily, Land Development and Commercial Properties [Member] \| Western United States [Member] \| Multifamily [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property		5
Multifamily, Land Development and Commercial Properties [Member] \| Western United States [Member] \| Commercial [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property		1
Multifamily, Land Development and Commercial Properties [Member] \| Western United States [Member] \| Development Properties [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property		3
Residential Property Acquired [Member] \| United Kingdom [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land		$ 4.2
Building		0.0
Acquired in place lease values		0.0
Investment debt		0.0
KWH Shareholders' Equity		$ 4.2
Residential Property Acquired [Member] \| United Kingdom [Member] \| Residential Real Estate [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property		1
Multifamily Property Acquired [Member] \| Ireland [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land		$ 11.1
Building		96.0
Acquired in place lease values		2.1
Investment debt		61.3
KWH Shareholders' Equity		$ 47.9
Multifamily Property Acquired [Member] \| Ireland [Member] \| Multifamily [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property		1

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Amount of facility held for productive use including, but not limited to, office, production, storage and distribution facilities, acquired at the acquisition date.

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