Real Estate and In-Place Lease Value - Schedule of Acquisitions (Details) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($) property
Business Acquisition [Line Items]
Land	$ 61.1
Building	176.5
Acquired in place lease values	2.7
Investment debt	145.0
NCI	0.0
KWH Shareholders' Equity	$ 95.3
Multifamily and Commercial Property Acquired In Western U.S. [Member] \| Commercial [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Western U.S. [Member] \| Multifamily and Commercial Property Acquired In Western U.S. [Member]
Business Acquisition [Line Items]
Land	$ 45.8
Building	80.5
Acquired in place lease values	0.6
Investment debt	83.7
NCI	0.0
KWH Shareholders' Equity	$ 43.2
Western U.S. [Member] \| Multifamily and Commercial Property Acquired In Western U.S. [Member] \| Multifamily [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	2
United Kingdom [Member] \| Residential Property In United Kingdom [Member]
Business Acquisition [Line Items]
Land	$ 4.2
Building	0.0
Acquired in place lease values	0.0
Investment debt	0.0
NCI	0.0
KWH Shareholders' Equity	$ 4.2
United Kingdom [Member] \| Residential Property In United Kingdom [Member] \| Residential Property [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1
Ireland [Member] \| Multifamily Property Acquired [Member]
Business Acquisition [Line Items]
Land	$ 11.1
Building	96.0
Acquired in place lease values	2.1
Investment debt	61.3
NCI	0.0
KWH Shareholders' Equity	$ 47.9
Ireland [Member] \| Multifamily Property Acquired [Member] \| Multifamily [Member]
Business Acquisition [Line Items]
Number of properties acquired \| property	1

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Number of Properties Acquired

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This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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-Publisher FASB
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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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The amount of financial liabilities assumed (as defined) which have been recognized as of the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount of real estate acquired, at the acquisition date.

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