Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended					6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Mar. 31, 2013	Jun. 30, 2014		Jun. 30, 2013
Earnings Per Share [Abstract]
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ 36.3		$ (2.5)		$ (2.5)	$ 46.8		$ (6.1)
Net income allocated to participating securities	(1.2)		(0.2)			(1.8)		(0.5)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders, net of allocation to participating securities	35.1		(2.7)			45.0		(6.6)
Dividends declared on common shares	(8.0)		(5.0)			(16.0)		(9.8)
Undistributed earnings attributable to Kennedy-Wilson Holdings, Inc. common shareholders, net of allocation to participating securities	$ 27.1		$ (7.7)			$ 29.0		$ (16.4)
Distributed earnings per share (in dollars per share)	$ 0.09		$ 0.07			$ 0.18		$ 0.14
Undistributed earnings per share (in dollars per share)	$ 0.30		$ (0.10)			$ 0.33		$ (0.23)
Income (loss) per basic (in dollars per share)	$ 0.39		$ (0.03)			$ 0.51		$ (0.09)
Income (loss) per diluted (in dollars per share)	$ 0.38		$ (0.03)			$ 0.50		$ (0.09)
Weighted average shares outstanding for basic (in shares)	89,140,498		70,976,247			88,645,002		66,432,823
Weighted average shares outstanding for diluted (in shares)	102,115,350	[1]	70,976,247	[1]		101,435,250	[1]	66,432,823	[1]
Dividends declared per common share (in dollars per share)	$ 0.09		$ 0.07			$ 0.18		$ 0.14
Potentially dilutive securities (in shares)			19,507,357					19,775,968

[1] For the three and six months ended June 30, 2013, a total of 19,507,357 and 19,775,968 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.