Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Total revenue	$ 106.5	$ 114.2	$ 106.9	$ 123.3	$ 142.3	$ 143.0	$ 143.7	$ 140.7	$ 450.9	$ 569.7	$ 772.4
Expenses
General and administrative									34.6	42.4	50.8
Depreciation and amortization									179.6	187.6	206.1
Total expenses	149.0	116.3	115.8	129.8	155.0	147.9	143.8	153.1	510.9	599.8	766.4
Income from unconsolidated investments, net of depreciation and amortization									81.0	179.7	78.7
Gain on sale of real estate, net									338.0	434.4	371.8
Gain on sale of business									0.0	0.0	40.4
Transaction-related expenses									(0.9)	(6.8)	(1.7)
Interest expense									(211.2)	(215.1)	(238.2)
Other income									4.5	0.4	13.1
Income before provision for income taxes	226.4	(32.5)	(42.3)	(0.2)	165.2	29.6	162.1	5.6	151.4	362.5	270.1
Provision for income taxes	(53.9)	12.8	3.2	(5.7)	(6.3)	(10.2)	(20.9)	(4.0)	(43.6)	(41.4)	(58.0)
Net income	172.5	(19.7)	(39.1)	(5.9)	158.9	19.4	141.2	1.6	107.8	321.1	212.1
Net loss (income) attributable to the noncontrolling interests	1.8	(1.1)	1.3	0.3	1.6	1.3	(90.4)	(6.9)	2.3	(94.4)	(62.1)
Preferred dividends and accretion of preferred stock issuance costs	(4.3)	(4.3)	(4.3)	(4.3)	(2.6)	0.0	0.0	0.0	(17.2)	(2.6)
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ 170.0	$ (25.1)	$ (42.1)	$ (9.9)	$ 157.9	$ 20.7	$ 50.8	$ (5.3)	$ 92.9	$ 224.1	$ 150.0
Basic Earnings per share
Income per basic (in dollars per share)	$ 1.23	$ (0.18)	$ (0.30)	$ (0.07)	$ 1.13	$ 0.15	$ 0.36	$ (0.04)	$ 0.66	$ 1.60	$ 1.04
Weighted average shares outstanding for basic (in shares)									139,741,411	139,729,573	142,895,472
Diluted Earnings per share
Income per diluted (in dollars per share)	$ 1.21	$ (0.18)	$ (0.30)	$ (0.07)	$ 1.12	$ 0.15	$ 0.36	$ (0.04)	$ 0.66	$ 1.58	$ 1.04
Weighted average shares outstanding for diluted (in shares)									140,347,365	141,501,323	144,753,421
Dividends declared per common share (in dollars per share)									$ 0.88	$ 0.85	$ 0.78
Rental
Revenue
Total revenue									$ 403.9	$ 447.4	$ 514.6
Expenses
Cost of goods sold									135.7	152.9	160.8
Hotel
Revenue
Total revenue									13.9	80.5	155.7
Expenses
Cost of goods sold									13.8	60.1	121.5
Sale of real estate
Revenue
Total revenue									0.0	1.1	56.8
Expenses
Cost of goods sold									0.0	1.2	52.5
Investment management, property services and research fees
Revenue
Total revenue									33.1	40.7	45.3
Commission and marketing
Expenses
Cost of goods sold									2.8	3.8	5.9
Compensation and related
Expenses
Cost of goods sold									$ 144.4	$ 151.8	$ 168.8