Guarantor and Non-Guarantor Financial Statements - Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue
Total revenue	$ 123.3	$ 140.7
Expenses
General and administrative	9.5	10.9
Depreciation and amortization	45.5	49.1
Total expenses	129.8	153.1
Income from unconsolidated investments	10.9	41.7
Income from consolidated subsidiaries	0.0	0.0
Non-operating income (expense)
Gain on sale of real estate	44.2	34.9
Transaction-related expenses	(0.2)	(0.8)
Interest expense	(48.8)	(55.3)
Other income (loss)	0.2	(2.5)
(Loss) income before provision for income taxes	(0.2)	5.6
Benefit from (provision for) income taxes	(5.7)	(4.0)
Net (loss) income	(5.9)	1.6
Net loss (income) attributable to the noncontrolling interests	0.3	(6.9)
Preferred dividends and accretion of preferred stock issuance costs	(4.3)	0.0
Net loss attributable to Kennedy-Wilson Holdings, Inc. common shareholders	(9.9)	(5.3)
Rental [Member]
Revenue
Total revenue	107.7	115.8
Expenses
Cost of goods and services	36.7	41.0
Hotel [Member]
Revenue
Total revenue	7.2	15.0
Expenses
Cost of goods and services	6.0	14.6
Sale of Real Estate [Member]
Revenue
Total revenue	0.0	1.1
Expenses
Cost of goods and services	0.0	1.2
Investment Management and Property Services Fees [Member]
Revenue
Total revenue	8.4	8.8
Commission and Marketing [Member]
Expenses
Cost of goods and services	0.7	1.0
Compensation and Related [Member]
Expenses
Cost of goods and services	31.4	35.3
Reportable Legal Entities [Member] | Parent [Member]
Revenue
Total revenue	0.0	0.0
Expenses
General and administrative	0.0	0.0
Depreciation and amortization	0.0	0.0
Total expenses	8.9	10.4
Income from unconsolidated investments	0.0	0.0
Income from consolidated subsidiaries	2.9	12.0
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0
Transaction-related expenses	0.0	0.0
Interest expense	0.0	0.0
Other income (loss)	0.0	0.0
(Loss) income before provision for income taxes	(6.0)	1.6
Benefit from (provision for) income taxes	0.0	0.0
Net (loss) income	(6.0)	1.6
Net loss (income) attributable to the noncontrolling interests	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs	(4.3)
Net loss attributable to Kennedy-Wilson Holdings, Inc. common shareholders	(10.3)	1.6
Reportable Legal Entities [Member] | Parent [Member] | Rental [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Parent [Member] | Hotel [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Parent [Member] | Sale of Real Estate [Member]
Revenue
Total revenue		0.0
Expenses
Cost of goods and services		0.0
Reportable Legal Entities [Member] | Parent [Member] | Investment Management and Property Services Fees [Member]
Revenue
Total revenue	0.0	0.0
Reportable Legal Entities [Member] | Parent [Member] | Commission and Marketing [Member]
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Parent [Member] | Compensation and Related [Member]
Expenses
Cost of goods and services	8.9	10.4
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Revenue
Total revenue	0.0	0.0
Expenses
General and administrative	4.8	5.0
Depreciation and amortization	0.4	0.3
Total expenses	15.0	19.1
Income from unconsolidated investments	(1.0)	0.2
Income from consolidated subsidiaries	33.9	50.7
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0
Transaction-related expenses	0.0	0.0
Interest expense	(15.4)	(18.2)
Other income (loss)	0.9	0.3
(Loss) income before provision for income taxes	3.4	13.9
Benefit from (provision for) income taxes	(0.6)	(1.9)
Net (loss) income	2.8	12.0
Net loss (income) attributable to the noncontrolling interests	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs	0.0
Net loss attributable to Kennedy-Wilson Holdings, Inc. common shareholders	2.8	12.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Rental [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Hotel [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Sale of Real Estate [Member]
Revenue
Total revenue		0.0
Expenses
Cost of goods and services		0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Investment Management and Property Services Fees [Member]
Revenue
Total revenue	0.0	0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Commission and Marketing [Member]
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Compensation and Related [Member]
Expenses
Cost of goods and services	9.8	13.8
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Revenue
Total revenue	55.9	50.5
Expenses
General and administrative	3.3	4.3
Depreciation and amortization	19.4	15.1
Total expenses	52.2	45.3
Income from unconsolidated investments	(2.8)	0.8
Income from consolidated subsidiaries	45.5	56.0
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0
Transaction-related expenses	0.0	(0.1)
Interest expense	(12.7)	(12.1)
Other income (loss)	0.0	0.1
(Loss) income before provision for income taxes	33.7	49.9
Benefit from (provision for) income taxes	0.2	0.8
Net (loss) income	33.9	50.7
Net loss (income) attributable to the noncontrolling interests	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs	0.0
Net loss attributable to Kennedy-Wilson Holdings, Inc. common shareholders	33.9	50.7
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Rental [Member]
Revenue
Total revenue	48.3	42.3
Expenses
Cost of goods and services	17.6	15.2
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Hotel [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Sale of Real Estate [Member]
Revenue
Total revenue		0.0
Expenses
Cost of goods and services		0.0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Investment Management and Property Services Fees [Member]
Revenue
Total revenue	7.6	8.2
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Commission and Marketing [Member]
Expenses
Cost of goods and services	0.7	1.0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Compensation and Related [Member]
Expenses
Cost of goods and services	11.2	9.7
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member]
Revenue
Total revenue	67.4	90.2
Expenses
General and administrative	1.4	1.6
Depreciation and amortization	25.7	33.7
Total expenses	53.7	78.3
Income from unconsolidated investments	14.7	40.7
Income from consolidated subsidiaries	0.0	0.0
Non-operating income (expense)
Gain on sale of real estate	44.2	34.9
Transaction-related expenses	(0.2)	(0.7)
Interest expense	(20.7)	(25.0)
Other income (loss)	(0.7)	(2.9)
(Loss) income before provision for income taxes	51.0	58.9
Benefit from (provision for) income taxes	(5.3)	(2.9)
Net (loss) income	45.7	56.0
Net loss (income) attributable to the noncontrolling interests	0.3	(6.9)
Preferred dividends and accretion of preferred stock issuance costs	0.0
Net loss attributable to Kennedy-Wilson Holdings, Inc. common shareholders	46.0	49.1
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Rental [Member]
Revenue
Total revenue	59.4	73.5
Expenses
Cost of goods and services	19.1	25.8
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Hotel [Member]
Revenue
Total revenue	7.2	15.0
Expenses
Cost of goods and services	6.0	14.6
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Sale of Real Estate [Member]
Revenue
Total revenue		1.1
Expenses
Cost of goods and services		1.2
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Investment Management and Property Services Fees [Member]
Revenue
Total revenue	0.8	0.6
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Commission and Marketing [Member]
Expenses
Cost of goods and services	0.0	0.0
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Compensation and Related [Member]
Expenses
Cost of goods and services	1.5	1.4
Elimination [Member]
Revenue
Total revenue	0.0	0.0
Expenses
General and administrative	0.0	0.0
Depreciation and amortization	0.0	0.0
Total expenses	0.0	0.0
Income from unconsolidated investments	0.0	0.0
Income from consolidated subsidiaries	(82.3)	(118.7)
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0
Transaction-related expenses	0.0	0.0
Interest expense	0.0	0.0
Other income (loss)	0.0	0.0
(Loss) income before provision for income taxes	(82.3)	(118.7)
Benefit from (provision for) income taxes	0.0	0.0
Net (loss) income	(82.3)	(118.7)
Net loss (income) attributable to the noncontrolling interests	0.0	0.0
Preferred dividends and accretion of preferred stock issuance costs	0.0
Net loss attributable to Kennedy-Wilson Holdings, Inc. common shareholders	(82.3)	(118.7)
Elimination [Member] | Rental [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Elimination [Member] | Hotel [Member]
Revenue
Total revenue	0.0	0.0
Expenses
Cost of goods and services	0.0	0.0
Elimination [Member] | Sale of Real Estate [Member]
Revenue
Total revenue		0.0
Expenses
Cost of goods and services		0.0
Elimination [Member] | Investment Management and Property Services Fees [Member]
Revenue
Total revenue	0.0	0.0
Elimination [Member] | Commission and Marketing [Member]
Expenses
Cost of goods and services	0.0	0.0
Elimination [Member] | Compensation and Related [Member]
Expenses
Cost of goods and services	$ 0.0	$ 0.0