Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share [Abstract]
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ 39.0	$ (9.0)	$ (1.8)	$ 25.8
Weighted average shares outstanding for basic (in shares)	139,389,170	136,840,417	138,674,109	136,828,876
(Loss) income per share (in dollars per share)	$ 0.28	$ (0.07)	$ (0.01)	$ 0.19
Weighted average shares outstanding (in shares)	139,545,944	136,840,417	138,674,109	137,115,950
Loss (income) per share (in dollars per share)	$ 0.28	$ (0.07)	$ (0.01)	$ 0.19
Potentially dilutive securities (in shares)	41,616,847	28,615,806	41,894,133	28,444,127