Real Estate and In-Place Lease Value - Schedule of Acquisitions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Business Acquisition [Line Items]
Land	$ 282.3
Building	460.6
Acquired in place lease values	76.7
Investment debt	524.0
NCI	242.4
KWH Shareholders' Equity	53.2
Acquisition-related gains	4.2	84.2
Commercial Acquired in United Kingdom [Member]
Business Acquisition [Line Items]
Land	265.5
Building	407.8
Acquired in place lease values	73.6
Investment debt	512.0
NCI	197.3
KWH Shareholders' Equity	37.6
Number of properties acquired	171
Commercial Acquired in Ireland [Member]
Business Acquisition [Line Items]
Land	11.1
Building	40.1
Acquired in place lease values	2.5
Investment debt	0
NCI	44.9
KWH Shareholders' Equity	8.8
Square feet of property acquired	75,500
Commercial Acquired in Western U.S. [Member]
Business Acquisition [Line Items]
Land	5.7
Building	12.7
Acquired in place lease values	0.6
Investment debt	12.0
NCI	0.2
KWH Shareholders' Equity	6.8
Square feet of property acquired	94,500
KWE [Member]
Business Acquisition [Line Items]
Acquisition-related gains	4.2
KWE [Member] \| Commercial Acquired in Ireland [Member]
Business Acquisition [Line Items]
Acquisition-related gains	$ 4.2
KWE [Member]
Business Acquisition [Line Items]
Ownership percentage by parent	16.00%

Business Combination, Equity Interest in Acquiree

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- Definition

Number of Properties Acquired

+ References

No definition available.

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- Definition

Number of Square feet of Retail Acquired

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- Definition

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

+ References

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- Definition

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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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

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-Glossary Financial Liability

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

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- Definition

Amount of real estate acquired, at the acquisition date.

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- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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