Equity - Noncontrolling Interests (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Noncontrolling interests	$ 1,805.7	$ 2,142.8
Distributions to noncontrolling interests	205.8
Contributions from noncontrolling interests	6.5
Acquisition of Kennedy Wilson Europe (KWE) shares from noncontrolling interest holders	59.5
KWE [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interests	$ 1,600.0
Ownership percentage by parent	17.70%
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interests	$ 1,800.0	$ 2,100.0
Foreign currency losses, net of hedges allocated to noncontrolling interest holders	63.3
Distributions to noncontrolling interests	205.8
Contributions from noncontrolling interests	6.5
Acquisition of Kennedy Wilson Europe (KWE) shares from noncontrolling interest holders	$ 59.5

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Paragraph 1

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Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders.

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to noncontrolling interests.

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