Guarantor and Non-Guarantor Financial Statements - Income Statements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenue
Investment management, property services and research fees	$ 15.1	$ 12.9	$ 47.0	$ 65.0
Rental	106.6	70.6	295.3	124.4
Hotel	31.3	22.9	78.0	36.9
Sale of real estate	1.6	1.6	3.7	19.0
Loan purchases, loan originations and other	4.6	5.7	13.4	11.7
Total revenue	159.2	113.7	437.4	257.0
Operating expenses
Commission and marketing	1.2	2.0	4.4	3.8
Rental operating	29.4	20.9	78.5	37.8
Hotel operating	22.7	16.9	66.1	32.1
Cost of real estate sold	1.1	1.1	2.6	14.6
Compensation and related	35.2	26.8	105.4	79.6
General and administrative	10.0	11.8	31.3	28.3
Depreciation and amortization	44.9	34.7	119.5	67.3
Total operating expenses	144.5	114.2	407.8	263.5
Income from unconsolidated investments	15.9	12.1	44.1	45.9
Income from consolidated subsidiaries	0.0	0.0	0.0	0.0
Operating income	30.6	11.6	73.7	39.4
Non-operating income (expense)
Acquisition-related gains	29.9	28.9	87.2	199.2
Acquisition-related expenses	(8.2)	(5.3)	(28.3)	(16.9)
Interest expense-investment	(31.3)	(13.8)	(77.9)	(30.2)
Interest expense-corporate	(11.7)	(15.9)	(35.5)	(41.1)
Gain on sale of real estate	4.6	0.0	44.7	0.0
Other income / (expense)	(4.3)	(1.9)	(0.7)	1.0
Income before provision for income taxes	9.6	3.6	63.2	151.4
(Provision for) benefit from income taxes	(4.5)	(6.6)	(32.5)	(40.8)
Net income (loss)	5.1	(3.0)	30.7	110.6
Net (income) loss attributable to the noncontrolling interests	10.3	2.8	15.0	(59.9)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc.	15.4	(0.2)	45.7	50.7
Preferred dividends and accretion of preferred stock issuance costs	(0.5)	(2.0)	(3.1)	(6.1)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	14.9	(2.2)	42.6	44.6
Parent [Member]
Revenue
Investment management, property services and research fees	0.0	0.0	0.0	0.0
Rental	0.0	0.0	0.0	0.0
Hotel	0.0	0.0	0.0	0.0
Sale of real estate	0.0	0.0	0.0	0.0
Loan purchases, loan originations and other	0.0	0.0	0.0	0.0
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Commission and marketing	0.0	0.0	0.0	0.0
Rental operating	0.0	0.0	0.0	0.0
Hotel operating	0.0	0.0	0.0	0.0
Cost of real estate sold	0.0	0.0	0.0	0.0
Compensation and related	5.5	5.3	19.6	8.7
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	5.5	5.3	19.6	8.7
Income from unconsolidated investments	0.0	0.0	0.0	0.0
Income from consolidated subsidiaries	10.6	2.3	50.3	119.3
Operating income	5.1	(3.0)	30.7	110.6
Non-operating income (expense)
Acquisition-related gains	0.0	0.0	0.0	0.0
Acquisition-related expenses	0.0	0.0	0.0	0.0
Interest expense-investment	0.0	0.0	0.0	0.0
Interest expense-corporate	0.0	0.0	0.0	0.0
Gain on sale of real estate	0.0	0.0	0.0
Other income / (expense)	0.0	0.0	0.0	0.0
Income before provision for income taxes	5.1	(3.0)	30.7	110.6
(Provision for) benefit from income taxes	0.0	0.0	0.0	0.0
Net income (loss)	5.1	(3.0)	30.7	110.6
Net (income) loss attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc.	5.1	(3.0)	30.7	110.6
Preferred dividends and accretion of preferred stock issuance costs	(0.5)	(2.0)	(3.1)	(6.1)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	4.6	(5.0)	27.6	104.5
Kennedy-Wilson, Inc. [Member]
Revenue
Investment management, property services and research fees	0.0	(0.5)	0.0	0.0
Rental	0.0	0.0	0.0	0.0
Hotel	0.0	0.0	0.0	0.0
Sale of real estate	0.0	0.0	0.0	0.0
Loan purchases, loan originations and other	0.0	0.1	0.0	0.2
Total revenue	0.0	(0.4)	0.0	0.2
Operating expenses
Commission and marketing	0.0	0.0	1.0	0.0
Rental operating	0.0	0.0	0.0	0.0
Hotel operating	0.0	0.0	0.0	0.0
Cost of real estate sold	0.0	0.0	0.0	0.0
Compensation and related	17.0	8.8	46.9	39.0
General and administrative	3.6	3.8	11.0	9.4
Depreciation and amortization	0.1	0.2	0.5	0.7
Total operating expenses	20.7	12.8	59.4	49.1
Income from unconsolidated investments	(1.2)	2.1	0.0	3.3
Income from consolidated subsidiaries	44.0	35.7	148.7	245.2
Operating income	22.1	24.6	89.3	199.6
Non-operating income (expense)
Acquisition-related gains	0.0	0.0	0.0	(7.0)
Acquisition-related expenses	(0.1)	0.0	(0.4)	0.0
Interest expense-investment	0.0	0.0	0.0	0.0
Interest expense-corporate	(11.7)	(15.9)	(35.5)	(41.1)
Gain on sale of real estate	0.0	0.0	0.0
Other income / (expense)	0.4	(0.2)	0.3	0.0
Income before provision for income taxes	10.7	8.5	53.7	151.5
(Provision for) benefit from income taxes	(0.1)	(6.1)	(3.4)	(32.2)
Net income (loss)	10.6	2.4	50.3	119.3
Net (income) loss attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc.	10.6	2.4	50.3	119.3
Preferred dividends and accretion of preferred stock issuance costs	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	10.6	2.4	50.3	119.3
Guarantor Subsidiaries [Member]
Revenue
Investment management, property services and research fees	14.7	14.1	44.9	62.6
Rental	19.2	5.6	44.0	12.0
Hotel	0.0	0.0	0.0	0.0
Sale of real estate	0.1	0.1	0.1	0.7
Loan purchases, loan originations and other	0.2	(2.8)	1.0	1.5
Total revenue	34.2	17.0	90.0	76.8
Operating expenses
Commission and marketing	1.1	1.6	2.7	3.0
Rental operating	8.0	(5.5)	16.2	(3.1)
Hotel operating	0.0	0.0	0.0	0.0
Cost of real estate sold	0.0	0.0	0.0	0.7
Compensation and related	11.0	10.7	32.4	27.0
General and administrative	4.9	7.5	12.2	11.5
Depreciation and amortization	5.7	3.1	14.2	7.9
Total operating expenses	30.7	17.4	77.7	47.0
Income from unconsolidated investments	20.0	4.2	37.6	35.1
Income from consolidated subsidiaries	(35.0)	30.2	49.0	183.1
Operating income	(11.5)	34.0	98.9	248.0
Non-operating income (expense)
Acquisition-related gains	61.6	0.0	61.6	3.7
Acquisition-related expenses	(0.4)	(0.1)	(0.6)	(1.7)
Interest expense-investment	(4.6)	(3.5)	(10.1)	(3.5)
Interest expense-corporate	0.0	0.0	0.0	0.0
Gain on sale of real estate	0.0	0.0	0.0
Other income / (expense)	0.1	0.0	0.1	1.5
Income before provision for income taxes	45.2	30.4	149.9	248.0
(Provision for) benefit from income taxes	(1.2)	5.1	(1.2)	(3.0)
Net income (loss)	44.0	35.5	148.7	245.0
Net (income) loss attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc.	44.0	35.5	148.7	245.0
Preferred dividends and accretion of preferred stock issuance costs	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	44.0	35.5	148.7	245.0
Non-Guarantor Subsidiaries [Member]
Revenue
Investment management, property services and research fees	0.4	(0.7)	2.1	2.4
Rental	87.4	65.0	251.3	112.4
Hotel	31.3	22.9	78.0	36.9
Sale of real estate	1.5	1.5	3.6	18.3
Loan purchases, loan originations and other	4.4	8.4	12.4	10.0
Total revenue	125.0	97.1	347.4	180.0
Operating expenses
Commission and marketing	0.1	0.4	0.7	0.8
Rental operating	21.4	26.4	62.3	40.9
Hotel operating	22.7	16.9	66.1	32.1
Cost of real estate sold	1.1	1.1	2.6	13.9
Compensation and related	1.7	2.0	6.5	4.9
General and administrative	1.5	0.5	8.1	7.4
Depreciation and amortization	39.1	31.4	104.8	58.7
Total operating expenses	87.6	78.7	251.1	158.7
Income from unconsolidated investments	(2.9)	5.8	6.5	7.5
Income from consolidated subsidiaries	0.0	0.0	0.0	0.0
Operating income	34.5	24.2	102.8	28.8
Non-operating income (expense)
Acquisition-related gains	(31.7)	28.9	25.6	202.5
Acquisition-related expenses	(7.7)	(5.2)	(27.3)	(15.2)
Interest expense-investment	(26.7)	(10.3)	(67.8)	(26.7)
Interest expense-corporate	0.0	0.0	0.0	0.0
Gain on sale of real estate	4.6	0.0	44.7
Other income / (expense)	(4.8)	(1.7)	(1.1)	(0.5)
Income before provision for income taxes	(31.8)	35.9	76.9	188.9
(Provision for) benefit from income taxes	(3.2)	(5.6)	(27.9)	(5.6)
Net income (loss)	(35.0)	30.3	49.0	183.3
Net (income) loss attributable to the noncontrolling interests	10.3	2.8	15.0	(59.9)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc.	(24.7)	33.1	64.0	123.4
Preferred dividends and accretion of preferred stock issuance costs	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	(24.7)	33.1	64.0	123.4
Elimination [Member]
Revenue
Investment management, property services and research fees	0.0	0.0	0.0	0.0
Rental	0.0	0.0	0.0	0.0
Hotel	0.0	0.0	0.0	0.0
Sale of real estate	0.0	0.0	0.0	0.0
Loan purchases, loan originations and other	0.0	0.0	0.0	0.0
Total revenue	0.0	0.0	0.0	0.0
Operating expenses
Commission and marketing	0.0	0.0	0.0	0.0
Rental operating	0.0	0.0	0.0	0.0
Hotel operating	0.0	0.0	0.0	0.0
Cost of real estate sold	0.0	0.0	0.0	0.0
Compensation and related	0.0	0.0	0.0	0.0
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	(19.6)	(68.2)	(248.0)	(547.6)
Operating income	(19.6)	(68.2)	(248.0)	(547.6)
Non-operating income (expense)
Acquisition-related gains	0.0	0.0	0.0	0.0
Acquisition-related expenses	0.0	0.0	0.0	0.0
Interest expense-investment	0.0	0.0	0.0	0.0
Interest expense-corporate	0.0	0.0	0.0	0.0
Gain on sale of real estate	0.0	0.0	0.0
Other income / (expense)	0.0	0.0	0.0	0.0
Income before provision for income taxes	(19.6)	(68.2)	(248.0)	(547.6)
(Provision for) benefit from income taxes	0.0	0.0	0.0	0.0
Net income (loss)	(19.6)	(68.2)	(248.0)	(547.6)
Net (income) loss attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc.	(19.6)	(68.2)	(248.0)	(547.6)
Preferred dividends and accretion of preferred stock issuance costs	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ (19.6)	$ (68.2)	$ (248.0)	$ (547.6)