REAL ESTATE AND ACQUIRED IN PLACE LEASE VALUE - Schedule of Consolidated Acquisitions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) property	Dec. 31, 2021 USD ($) property
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 124.7	$ 262.0
Building	470.7	842.2
Acquired in place lease values	8.3	24.6
Investment debt	203.4	469.1
KWH Shareholders' Equity	$ 400.3	$ 659.7
Western U.S. | Multifamily
Business Acquisition [Line Items]
Number of properties acquired | property	4	10
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	$ 99.2	$ 166.1
Building	396.6	610.9
Acquired in place lease values	1.4	2.3
Investment debt	203.4	469.1
KWH Shareholders' Equity	293.8	$ 310.2
United Kingdom
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land	25.5
Building	74.1
Acquired in place lease values	6.9
Investment debt	0.0
KWH Shareholders' Equity	$ 106.5
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