EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ 157.9	$ 20.7	$ 50.8	$ (5.3)	$ 30.7	$ 12.1	$ 109.6	$ (2.4)	$ 224.1	$ 150.0	$ 100.5
Net income and dividends allocated to participating securities									(0.3)	(0.9)	(1.1)
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders, net of allocation to participating securities									223.8	149.1	99.4
Dividends declared on common shares									(121.1)	(113.0)	(86.5)
Undistributed earnings attributable to Kennedy-Wilson Holdings, Inc. common shareholders									$ 102.7	$ 36.1	$ 12.9
Distributed earnings per share (in dollars per share)									$ 0.85	$ 0.78	$ 0.70
Undistributed earnings per share (in dollars per share)									0.75	0.26	0.13
Income per basic (in dollars per share)	$ 1.13	$ 0.15	$ 0.36	$ (0.04)	$ 0.21	$ 0.09	$ 0.77	$ (0.02)	1.60	1.04	0.83
Income per diluted (in dollars per share)	$ 1.12	$ 0.15	$ 0.36	$ (0.04)	$ 0.21	$ 0.09	$ 0.77	$ (0.02)	$ 1.58	$ 1.04	$ 0.83
Weighted average shares outstanding for basic (in shares)									139,729,573	142,895,472	119,147,192
Weighted average shares outstanding for diluted (in shares)									141,501,323	144,753,421	119,147,192
Dividends declared per common share (in dollars per share)									$ 0.85	$ 0.78	$ 0.70
Potentially dilutive securities (in shares)									13,133,785	0	1,080,092