Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Earnings Per Share [Abstract]
Net (loss) income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ (2.2)		$ (4.1)		$ 44.6		$ (10.2)
Net income and dividends allocated to participating securities	(0.5)		0		(2.6)		0
Net (loss) income attributable to Kennedy-Wilson Holdings, Inc. common shareholders, net of allocation to participating securities	(2.7)		(4.1)		42.0		(10.2)
Dividends declared on common shares	(8.1)		(15.2)		(24.1)		(5.5)
Undistributed (losses) earnings attributable to Kennedy-Wilson Holdings, Inc. common shareholders, net of allocation to participating securities	$ (10.8)		$ (19.3)		$ 17.9		$ (15.7)
Distributed earnings per share (in dollars per share)	$ 0.09		$ 0.07		$ 0.27		$ 0.21
Undistributed earnings per share (in dollars per share)	$ (0.12)		$ (0.13)		$ 0.20		$ (0.36)
Income (loss) per basic (in dollars per share)	$ (0.03)		$ (0.06)		$ 0.47		$ (0.15)
Income (loss) per diluted (in dollars per share)	$ (0.03)		$ (0.06)		$ 0.47		$ (0.15)
Weighted average shares outstanding for basic (in shares)	89,267,838		72,643,000		88,854,215		68,486,876
Weighted average shares outstanding for diluted (in shares)	89,267,838	[1]	72,643,000	[1]	90,169,008	[1]	68,486,876	[1]
Dividends declared per common share (in dollars per share)	$ 0.09		$ 0.07		$ 0.27		$ 0.21
Potentially dilutive securities (in shares)	12,993,531		19,315,303				19,620,824

[1] For the three months ended September 30, 2014, a total of 12,993,531 potentially dilutive securities have not been included in the diluted weighted average shares as they are anti-dilutive. For the three and nine months ended September 30, 2013, a total of 19,315,303 and 19,620,824 potentially dilutive securities have not been included in the diluted weighted average shares as they are anti-dilutive. Potentially anti-dilutive securities include preferred stock, warrants, and unvested restricted stock grants.