GUARANTOR AND NON-GUARANTOR FINANCIAL STATEMENTS - Consolidating Statement of Income (Details) - USD ($) $ 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
Condensed Financial Statements, Captions [Line Items]
Total revenue	$ 142.3	$ 143.0	$ 143.7	$ 140.7	$ 178.7	$ 185.8	$ 218.3	$ 190.7	$ 569.7	$ 772.4	$ 801.8
Expenses
General and administrative									42.4	50.8	42.2
Depreciation and amortization									187.6	206.1	212.5
Total expenses	155.0	147.9	143.8	153.1	187.8	177.2	212.5	188.9	599.8	766.4	770.8
Income from unconsolidated investments, net of depreciation and amortization	177.9	34.5	162.2	18.0	66.3	11.2	190.9	(5.4)	179.7	78.7	77.8
Income from consolidated subsidiaries									0.0	0.0	0.0
Gain on sale of real estate, net									434.4	371.8	226.7
Gain on sale of business									0.0	40.4	0.0
Acquisition -related gains										0.0	0.0
Acquisition-related expenses									(6.8)	(1.7)	(4.4)
Interest expense									(215.1)	(238.2)	(217.7)
Other income									0.4	13.1	8.3
Income before (provision for) benefit from income taxes	165.2	29.6	162.1	5.6	57.2	19.8	196.7	(3.6)	362.5	270.1	121.7
(Provision for) benefit from income taxes	(6.3)	(10.2)	(20.9)	(4.0)	(24.3)	(6.9)	(29.4)	2.6	(41.4)	(58.0)	16.3
Net income	158.9	19.4	141.2	1.6	32.9	12.9	167.3	(1.0)	321.1	212.1	138.0
Net (income) loss attributable to the noncontrolling interests	1.6	1.3	(90.4)	(6.9)	(2.2)	(0.8)	(57.7)	(1.4)	(94.4)	(62.1)	(37.5)
Preferred dividends and accretion of preferred stock issuance costs	(2.6)	0.0	0.0	0.0					(2.6)	0.0	0.0
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
Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Expenses
General and administrative									0.0	0.0	0.0
Depreciation and amortization									0.0	0.0	0.0
Total expenses									31.8	37.1	38.4
Income from unconsolidated investments, net of depreciation and amortization									0.0	0.0	0.0
Income from consolidated subsidiaries									352.8	249.2	176.4
Gain on sale of real estate, net									0.0	0.0	0.0
Gain on sale of business										0.0	0.0
Acquisition -related gains										0.0	0.0
Acquisition-related expenses									0.0	0.0	0.0
Interest expense									0.0	0.0	0.0
Other income									0.1	0.0	0.0
Income before (provision for) benefit from income taxes									321.1	212.1	138.0
(Provision for) benefit from income taxes									0.0	0.0	0.0
Net income									321.1	212.1	138.0
Net (income) loss attributable to the noncontrolling interests									0.0	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs									(2.6)	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders									318.5	212.1	138.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.8	0.0	0.0
Expenses
General and administrative									19.8	20.3	14.0
Depreciation and amortization									1.1	1.3	1.4
Total expenses									95.9	92.9	93.7
Income from unconsolidated investments, net of depreciation and amortization									0.1	(1.3)	3.7
Income from consolidated subsidiaries									547.7	451.3	307.5
Gain on sale of real estate, net									0.0	0.0	0.0
Gain on sale of business										0.0	0.0
Acquisition -related gains										0.0	0.0
Acquisition-related expenses									(3.1)	(0.1)	0.0
Interest expense									(69.5)	(77.1)	(72.1)
Other income									(0.3)	13.3	9.9
Income before (provision for) benefit from income taxes									379.8	293.2	155.3
(Provision for) benefit from income taxes									(26.9)	(44.0)	21.1
Net income									352.9	249.2	176.4
Net (income) loss attributable to the noncontrolling interests									0.0	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs									0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders									352.9	249.2	176.4
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									210.2	210.3	181.4
Expenses
General and administrative									15.9	21.2	17.6
Depreciation and amortization									62.5	56.9	50.1
Total expenses									185.7	201.4	184.0
Income from unconsolidated investments, net of depreciation and amortization									83.3	60.3	41.7
Income from consolidated subsidiaries									479.8	332.7	256.2
Gain on sale of real estate, net									8.2	61.4	46.6
Gain on sale of business										40.4	0.0
Acquisition -related gains										0.0	0.0
Acquisition-related expenses									(0.2)	(1.1)	(1.3)
Interest expense									(49.2)	(52.8)	(38.0)
Other income									0.2	0.1	1.6
Income before (provision for) benefit from income taxes									546.6	449.9	304.2
(Provision for) benefit from income taxes									1.1	1.4	3.3
Net income									547.7	451.3	307.5
Net (income) loss attributable to the noncontrolling interests									0.0	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs									0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders									547.7	451.3	307.5
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									358.7	562.1	620.4
Expenses
General and administrative									6.7	9.3	10.6
Depreciation and amortization									124.0	147.9	161.0
Total expenses									286.4	435.0	454.7
Income from unconsolidated investments, net of depreciation and amortization									96.3	19.7	32.4
Income from consolidated subsidiaries									0.0	0.0	0.0
Gain on sale of real estate, net									426.2	310.4	180.1
Gain on sale of business										0.0	0.0
Acquisition -related gains										0.0	0.0
Acquisition-related expenses									(3.5)	(0.5)	(3.1)
Interest expense									(96.4)	(108.3)	(107.6)
Other income									0.4	(0.3)	(3.2)
Income before (provision for) benefit from income taxes									495.3	348.1	264.3
(Provision for) benefit from income taxes									(15.6)	(15.4)	(8.1)
Net income									479.7	332.7	256.2
Net (income) loss attributable to the noncontrolling interests									(94.4)	(62.1)	(37.5)
Preferred dividends and accretion of preferred stock issuance costs									0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders									385.3	270.6	218.7
Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Expenses
General and administrative									0.0	0.0	0.0
Depreciation and amortization									0.0	0.0	0.0
Total expenses									0.0	0.0	0.0
Income from unconsolidated investments, net of depreciation and amortization									0.0	0.0	0.0
Income from consolidated subsidiaries									(1,380.3)	(1,033.2)	(740.1)
Gain on sale of real estate, net									0.0	0.0	0.0
Gain on sale of business										0.0	0.0
Acquisition -related gains										0.0	0.0
Acquisition-related expenses									0.0	0.0	0.0
Interest expense									0.0	0.0	0.0
Other income									0.0	0.0	0.0
Income before (provision for) benefit from income taxes									(1,380.3)	(1,033.2)	(740.1)
(Provision for) benefit from income taxes									0.0	0.0	0.0
Net income									(1,380.3)	(1,033.2)	(740.1)
Net (income) loss attributable to the noncontrolling interests									0.0	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs									0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders									(1,380.3)	(1,033.2)	(740.1)
Rental [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									447.4	514.6	504.7
Cost of goods sold									152.9	160.8	151.2
Rental [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Rental [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Rental [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									173.6	168.4	143.9
Cost of goods sold									64.3	62.3	54.7
Rental [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									273.8	346.2	360.8
Cost of goods sold									88.6	98.5	96.5
Rental [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Hotel [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									80.5	155.7	127.5
Cost of goods sold									60.1	121.5	100.3
Hotel [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Hotel [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Hotel [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Hotel [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									80.5	155.7	127.5
Cost of goods sold									60.1	121.5	100.3
Hotel [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Sale of real estate [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									1.1	56.8	111.5
Cost of goods sold									1.2	52.5	80.2
Sale of real estate [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Sale of real estate [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Sale of real estate [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	2.3
Cost of goods sold									0.0	0.0	1.8
Sale of real estate [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									1.1	56.8	109.2
Cost of goods sold									1.2	52.5	78.4
Sale of real estate [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Cost of goods sold									0.0	0.0	0.0
Investment management, property services and research fees [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									40.7	45.3	42.9
Investment management, property services and research fees [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Investment management, property services and research fees [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.8	0.0	0.0
Investment management, property services and research fees [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									36.6	41.9	34.7
Investment management, property services and research fees [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									3.3	3.4	8.2
Investment management, property services and research fees [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	0.0
Loan purchases, loan originations, and other [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									0.0	0.0	15.2
Loan purchases, loan originations, and other [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue											0.0
Loan purchases, loan originations, and other [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue											0.0
Loan purchases, loan originations, and other [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue											0.5
Loan purchases, loan originations, and other [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue											14.7
Loan purchases, loan originations, and other [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue											0.0
Commission and marketing [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									3.8	5.9	7.2
Commission and marketing [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									0.0	0.0	0.0
Commission and marketing [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									0.0	0.0	0.0
Commission and marketing [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									3.8	5.9	7.0
Commission and marketing [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									0.0	0.0	0.2
Commission and marketing [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									0.0	0.0	0.0
Compensation and related [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									151.8	168.8	177.2
Compensation and related [Member] | Reportable Legal Entities [Member] | Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									31.8	37.1	38.4
Compensation and related [Member] | Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									75.0	71.3	78.3
Compensation and related [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									39.2	55.1	52.8
Compensation and related [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									5.8	5.3	7.7
Compensation and related [Member] | Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of goods sold									$ 0.0	$ 0.0	$ 0.0