Guarantor and Non-Guarantor Financial Statements - Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue
Total revenue	$ 218.3	$ 180.4	$ 409.0	$ 348.0
Operating expenses
General and administrative	13.5	10.0	24.9	19.9
Depreciation and amortization	51.5	52.1	107.2	101.8
Total operating expenses	212.5	178.3	401.4	333.7
Income from unconsolidated investments	10.9	10.8	36.9	39.8
Income from consolidated subsidiaries	0.0	0.0	0.0	0.0
Operating income	16.7	12.9	44.5	54.1
Non-operating income (expense)
Gain on sale of real estate	236.8	66.3	264.8	71.7
Acquisition-related expenses	(0.2)	(0.9)	(0.2)	(1.2)
Interest expense	(67.2)	(52.1)	(126.1)	(102.1)
Other income (loss)	10.6	4.4	10.1	4.9
Income before provision for income taxes	196.7	30.6	193.1	27.4
Benefit from (provision for) income taxes	(29.4)	(8.8)	(26.8)	(4.6)
Net income	167.3	21.8	166.3	22.8
Net income attributable to the noncontrolling interests	(57.7)	(12.4)	(59.1)	(12.6)
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	109.6	9.4	107.2	10.2
Rental [Member]
Revenue
Total revenue	134.9	123.8	269.2	248.1
Operating expenses
Cost of goods and services	39.7	36.6	81.3	72.6
Hotel [Member]
Revenue
Total revenue	37.8	29.0	74.1	58.5
Operating expenses
Cost of goods and services	29.4	22.8	60.2	47.2
Sale of Real Estate [Member]
Revenue
Total revenue	32.8	12.8	42.2	13.6
Operating expenses
Cost of goods and services	31.4	9.6	39.8	10.3
Investment Management, Property Services and Research Fees [Member]
Revenue
Total revenue	12.3	10.3	22.4	21.3
Loan Purchases, Loan Originations and Other [Member]
Revenue
Total revenue	0.5	4.5	1.1	6.5
Commission and Marketing [Member]
Operating expenses
Cost of goods and services	2.1	1.7	3.5	3.7
Compensation and Related [Member]
Operating expenses
Cost of goods and services	44.9	45.5	84.5	78.2
Reportable Legal Entities [Member] \| Parent [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
General and administrative	0.0	0.0	0.0	0.0
Depreciation and amortization	0.0	0.0	0.0	0.0
Total operating expenses	8.8	9.4	18.7	20.1
Income from unconsolidated investments	0.0	0.0	0.0	0.0
Income from consolidated subsidiaries	176.1	31.2	185.0	42.9
Operating income	167.3	21.8	166.3	22.8
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0	0.0	0.0
Acquisition-related expenses	0.0	0.0	0.0	0.0
Interest expense	0.0	0.0	0.0	0.0
Other income (loss)	0.0	0.0	0.0	0.0
Income before provision for income taxes	167.3	21.8	166.3	22.8
Benefit from (provision for) income taxes	0.0	0.0	0.0	0.0
Net income	167.3	21.8	166.3	22.8
Net income attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	167.3	21.8	166.3	22.8
Reportable Legal Entities [Member] \| Parent [Member] \| Rental [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Parent [Member] \| Hotel [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Parent [Member] \| Sale of Real Estate [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Parent [Member] \| Investment Management, Property Services and Research Fees [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Parent [Member] \| Loan Purchases, Loan Originations and Other [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Parent [Member] \| Commission and Marketing [Member]
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Parent [Member] \| Compensation and Related [Member]
Operating expenses
Cost of goods and services	8.8	9.4	18.7	20.1
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
General and administrative	5.4	3.6	9.3	6.5
Depreciation and amortization	0.3	0.3	0.7	0.7
Total operating expenses	26.1	24.5	44.0	35.0
Income from unconsolidated investments	0.2	0.4	(0.7)	1.6
Income from consolidated subsidiaries	230.7	76.1	276.6	107.7
Operating income	204.8	52.0	231.9	74.3
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0	0.0	0.0
Acquisition-related expenses	0.0	(0.1)	0.0	(0.1)
Interest expense	(19.4)	(16.6)	(39.4)	(32.2)
Other income (loss)	10.2	3.4	10.0	3.2
Income before provision for income taxes	195.6	38.7	202.5	45.2
Benefit from (provision for) income taxes	(19.5)	(7.5)	(17.5)	(2.3)
Net income	176.1	31.2	185.0	42.9
Net income attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	176.1	31.2	185.0	42.9
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Rental [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Hotel [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Sale of Real Estate [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Investment Management, Property Services and Research Fees [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Loan Purchases, Loan Originations and Other [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Commission and Marketing [Member]
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Kennedy-Wilson, Inc. [Member] \| Compensation and Related [Member]
Operating expenses
Cost of goods and services	20.4	20.6	34.0	27.8
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Revenue
Total revenue	57.4	43.4	109.6	85.8
Operating expenses
General and administrative	5.7	3.3	10.7	7.8
Depreciation and amortization	14.4	12.0	29.2	23.6
Total operating expenses	52.9	44.2	102.4	88.1
Income from unconsolidated investments	7.4	0.8	23.6	14.2
Income from consolidated subsidiaries	176.0	39.7	213.5	66.3
Operating income	187.9	39.7	244.3	78.2
Non-operating income (expense)
Gain on sale of real estate	61.5	46.6	61.5	46.6
Acquisition-related expenses	0.0	(0.7)	0.0	(0.7)
Interest expense	(17.7)	(9.5)	(29.2)	(17.9)
Other income (loss)	0.1	0.1	0.0	0.1
Income before provision for income taxes	231.8	76.2	276.6	106.3
Benefit from (provision for) income taxes	(1.1)	(0.1)	0.0	1.4
Net income	230.7	76.1	276.6	107.7
Net income attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	230.7	76.1	276.6	107.7
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Rental [Member]
Revenue
Total revenue	46.4	35.2	89.1	68.3
Operating expenses
Cost of goods and services	16.3	13.6	29.8	26.8
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Hotel [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Sale of Real Estate [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Investment Management, Property Services and Research Fees [Member]
Revenue
Total revenue	11.0	8.2	20.4	17.2
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Loan Purchases, Loan Originations and Other [Member]
Revenue
Total revenue	0.0	0.0	0.1	0.3
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Commission and Marketing [Member]
Operating expenses
Cost of goods and services	2.1	1.7	3.5	3.6
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member] \| Compensation and Related [Member]
Operating expenses
Cost of goods and services	14.4	13.6	29.2	26.3
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member]
Revenue
Total revenue	160.9	137.0	299.4	262.2
Operating expenses
General and administrative	2.4	3.1	4.9	5.6
Depreciation and amortization	36.8	39.8	77.3	77.5
Total operating expenses	124.7	100.2	236.3	190.5
Income from unconsolidated investments	3.3	9.6	14.0	24.0
Income from consolidated subsidiaries	0.0	0.0	0.0	0.0
Operating income	39.5	46.4	77.1	95.7
Non-operating income (expense)
Gain on sale of real estate	175.3	19.7	203.3	25.1
Acquisition-related expenses	(0.2)	(0.1)	(0.2)	(0.4)
Interest expense	(30.1)	(26.0)	(57.5)	(52.0)
Other income (loss)	0.3	0.9	0.1	1.6
Income before provision for income taxes	184.8	40.9	222.8	70.0
Benefit from (provision for) income taxes	(8.8)	(1.2)	(9.3)	(3.7)
Net income	176.0	39.7	213.5	66.3
Net income attributable to the noncontrolling interests	(57.7)	(12.4)	(59.1)	(12.6)
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	118.3	27.3	154.4	53.7
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Rental [Member]
Revenue
Total revenue	88.5	88.6	180.1	179.8
Operating expenses
Cost of goods and services	23.4	23.0	51.5	45.8
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Hotel [Member]
Revenue
Total revenue	37.8	29.0	74.1	58.5
Operating expenses
Cost of goods and services	29.4	22.8	60.2	47.2
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Sale of Real Estate [Member]
Revenue
Total revenue	32.8	12.8	42.2	13.6
Operating expenses
Cost of goods and services	31.4	9.6	39.8	10.3
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Investment Management, Property Services and Research Fees [Member]
Revenue
Total revenue	1.3	2.1	2.0	4.1
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Loan Purchases, Loan Originations and Other [Member]
Revenue
Total revenue	0.5	4.5	1.0	6.2
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Commission and Marketing [Member]
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.1
Reportable Legal Entities [Member] \| Non-guarantor Subsidiaries [Member] \| Compensation and Related [Member]
Operating expenses
Cost of goods and services	1.3	1.9	2.6	4.0
Elimination [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
General and administrative	0.0	0.0	0.0	0.0
Depreciation and amortization	0.0	0.0	0.0	0.0
Total operating expenses	0.0	0.0	0.0	0.0
Income from unconsolidated investments	0.0	0.0	0.0	0.0
Income from consolidated subsidiaries	(582.8)	(147.0)	(675.1)	(216.9)
Operating income	(582.8)	(147.0)	(675.1)	(216.9)
Non-operating income (expense)
Gain on sale of real estate	0.0	0.0	0.0	0.0
Acquisition-related expenses	0.0	0.0	0.0	0.0
Interest expense	0.0	0.0	0.0	0.0
Other income (loss)	0.0	0.0	0.0	0.0
Income before provision for income taxes	(582.8)	(147.0)	(675.1)	(216.9)
Benefit from (provision for) income taxes	0.0	0.0	0.0	0.0
Net income	(582.8)	(147.0)	(675.1)	(216.9)
Net income attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	(582.8)	(147.0)	(675.1)	(216.9)
Elimination [Member] \| Rental [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Elimination [Member] \| Hotel [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Elimination [Member] \| Sale of Real Estate [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Elimination [Member] \| Investment Management, Property Services and Research Fees [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Elimination [Member] \| Loan Purchases, Loan Originations and Other [Member]
Revenue
Total revenue	0.0	0.0	0.0	0.0
Elimination [Member] \| Commission and Marketing [Member]
Operating expenses
Cost of goods and services	0.0	0.0	0.0	0.0
Elimination [Member] \| Compensation and Related [Member]
Operating expenses
Cost of goods and services	$ 0.0	$ 0.0	$ 0.0	$ 0.0

Income (Loss) from Consolidated Subsidiaries

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Income (Loss) From Unconsolidated Investments

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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Total costs of sales and operating expenses for the period.

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The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of expenses related to the generation of investment income.

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Amount of Net Income (Loss) attributable to noncontrolling interest.

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