REAL ESTATE AND ACQUIRED IN PLACE LEASE VALUE - Schedule of Consolidated Acquisitions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) property	Dec. 31, 2020 USD ($) property
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 262.0	$ 13.4
Building	842.2	95.1
Acquired in place lease values	24.6	0.5
Investment debt	469.1	38.7
KWH Shareholders' Equity	$ 659.7	$ 147.8
Western U.S. | Multifamily
Business Acquisition [Line Items]
Number of properties acquired | property	10	1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 166.1	$ 13.4
Building	610.9	53.6
Acquired in place lease values	2.3	0.5
Investment debt	469.1	38.7
KWH Shareholders' Equity	$ 310.2	$ 106.3
United Kingdom | Industrial
Business Acquisition [Line Items]
Number of properties acquired | property		1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land		$ 0.0
Building		40.2
Acquired in place lease values		0.0
Investment debt		0.0
KWH Shareholders' Equity		$ 40.2
United Kingdom | Commercial
Business Acquisition [Line Items]
Number of properties acquired | property	2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 95.9
Building	231.3
Acquired in place lease values	22.3
Investment debt	0.0
KWH Shareholders' Equity	$ 349.5
Ireland | Commercial
Business Acquisition [Line Items]
Number of properties acquired | property		1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land		$ 0.0
Building		1.3
Acquired in place lease values		0.0
Investment debt		0.0
KWH Shareholders' Equity		$ 1.3