Segment Information - Segment Information, by Segment (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) segment	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment				2
Revenue
Total revenue		$ 146.5	$ 136.1	$ 278.7	$ 260.8
Principal co-investments		6.3	39.4	22.7	117.6
Performance allocations		(7.7)	(8.7)	(18.4)	18.5
Total (loss) income from unconsolidated investments		(1.4)	30.7	4.3	136.1
Gain on sale of real estate, net		89.0	11.9	108.2	13.8
Expenses
Performance allocation compensation		(1.1)	(2.0)	0.5	9.8
General and administrative		8.7	9.4	17.1	17.3
Depreciation and amortization		40.1	43.3	79.5	86.6
Total expenses		133.1	128.5	257.6	267.6
Non-operating income (expense)
Interest expense		(66.0)	(53.2)	(128.3)	(103.7)
Gain (loss ) on extinguishment		(1.7)	(1.1)	(1.6)	(1.1)
Other income		24.3	3.6	21.3	9.4
Benefit from (provision for) income taxes		(10.3)	(0.4)	(6.4)	(8.6)
Net income		47.3	(0.9)	18.6	39.1
Net loss (income) attributable to the noncontrolling interests		0.1	(0.3)	(4.1)	(0.2)
Preferred dividends		(8.4)	(7.8)	(16.3)	(13.1)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders		39.0	(9.0)	(1.8)	25.8
Segment Reporting Information, Assets [Abstract]
Total assets	[1]	8,193.9		8,193.9		$ 8,271.8
Corporate
Revenue
Total revenue		0.6	0.4	0.9	0.8
Principal co-investments		0.0	0.0		0.0
Performance allocations		0.0	0.0		0.0
Total (loss) income from unconsolidated investments		0.0	0.0	0.0	0.0
Gain on sale of real estate, net		0.0	0.0
Expenses
Performance allocation compensation		0.0	0.0	0.0	0.0
General and administrative		1.9	1.9	3.5	3.6
Depreciation and amortization		0.0	0.0	0.0	0.0
Total expenses		15.4	15.0	29.4	30.2
Non-operating income (expense)
Interest expense		25.0	22.5	50.1	44.0
Gain (loss ) on extinguishment		0.0	0.0	0.0	0.0
Other income		11.3	0.8	9.3	3.5
Benefit from (provision for) income taxes		(4.1)	8.1	1.6	1.8
Net income		(32.6)	(28.2)	(67.7)	(68.1)
Net loss (income) attributable to the noncontrolling interests		0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders		(41.0)	(36.0)	(84.0)	(81.2)
Segment Reporting Information, Assets [Abstract]
Total assets		290.3		290.3		200.2
Rental
Revenue
Total revenue		106.6	109.3	213.2	213.5
Expenses
Cost of goods and services		38.7	36.4	75.3	72.1
Rental | Corporate
Revenue
Total revenue		0.0	0.0	0.0	0.0
Expenses
Cost of goods and services		0.0	0.0	0.0	0.0
Hotel
Revenue
Total revenue		15.5	12.7	26.1	19.2
Expenses
Cost of goods and services		9.7	7.6	17.6	11.9
Hotel | Corporate
Revenue
Total revenue		0.0	0.0	0.0	0.0
Expenses
Cost of goods and services		0.0	0.0	0.0	0.0
Investment management fees
Revenue
Total revenue		19.1	11.0	30.1	22.3
Investment management fees | Corporate
Revenue
Total revenue		0.0	0.0	0.0	0.0
Loans
Revenue
Total revenue		4.7	2.7	8.4	5.0
Loans | Corporate
Revenue
Total revenue		0.0	0.0	0.0	0.0
Compensation and related
Expenses
Cost of goods and services		37.0	33.8	67.6	69.9
Compensation and related | Corporate
Expenses
Cost of goods and services		13.5	13.1	25.9	26.6
Other Revenue
Revenue
Total revenue		0.6	0.4	0.9	0.8
Other Revenue | Corporate
Revenue
Total revenue		0.6	0.4	0.9	0.8
Consolidated | Operating Segments
Revenue
Total revenue		122.1	122.0	239.3	232.7
Principal co-investments		0.0	0.0		0.0
Performance allocations		0.0	0.0		0.0
Total (loss) income from unconsolidated investments		0.0	0.0	0.0	0.0
Gain on sale of real estate, net		89.0	11.9	108.2	13.8
Expenses
Performance allocation compensation		0.0	0.0	0.0	0.0
General and administrative		4.3	3.6	7.9	6.1
Depreciation and amortization		40.1	43.3	79.5	86.6
Total expenses		106.2	100.7	203.5	194.7
Non-operating income (expense)
Interest expense		(41.0)	(30.7)	(78.2)	(59.7)
Gain (loss ) on extinguishment		(1.7)	(1.1)	(1.6)	(1.1)
Other income		13.0	2.8	12.0	5.9
Benefit from (provision for) income taxes		(6.2)	(8.5)	(8.0)	(10.4)
Net income		69.0	(4.3)	68.2	(13.5)
Net loss (income) attributable to the noncontrolling interests		0.1	(0.3)	(4.1)	(0.2)
Preferred dividends		0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders		69.1	(4.6)	64.1	(13.7)
Segment Reporting Information, Assets [Abstract]
Total assets		5,338.6		5,338.6		5,684.1
Consolidated | Rental | Operating Segments
Revenue
Total revenue		106.6	109.3	213.2	213.5
Expenses
Cost of goods and services		38.7	36.4	75.3	72.1
Consolidated | Hotel | Operating Segments
Revenue
Total revenue		15.5	12.7	26.1	19.2
Expenses
Cost of goods and services		9.7	7.6	17.6	11.9
Consolidated | Investment management fees | Operating Segments
Revenue
Total revenue		0.0	0.0	0.0	0.0
Consolidated | Loans | Operating Segments
Revenue
Total revenue		0.0	0.0	0.0	0.0
Consolidated | Compensation and related | Operating Segments
Expenses
Cost of goods and services		13.4	9.8	23.2	18.0
Consolidated | Other Revenue | Operating Segments
Revenue
Total revenue		0.0	0.0	0.0	0.0
Co-Investments | Operating Segments
Revenue
Total revenue		23.8	13.7	38.5	27.3
Principal co-investments		6.3	39.4	22.7	117.6
Performance allocations		(7.7)	(8.7)	(18.4)	18.5
Total (loss) income from unconsolidated investments		(1.4)	30.7	4.3	136.1
Gain on sale of real estate, net		0.0	0.0	0.0	0.0
Expenses
Performance allocation compensation		(1.1)	(2.0)	0.5	9.8
General and administrative		2.5	3.9	5.7	7.6
Depreciation and amortization		0.0	0.0	0.0	0.0
Total expenses		11.5	12.8	24.7	42.7
Non-operating income (expense)
Interest expense		0.0	0.0	0.0	0.0
Gain (loss ) on extinguishment		0.0	0.0	0.0	0.0
Other income			0.0	0.0	0.0
Benefit from (provision for) income taxes		0.0	0.0	0.0	0.0
Net income		10.9	31.6	18.1	120.7
Net loss (income) attributable to the noncontrolling interests		0.0	0.0	0.0	0.0
Preferred dividends		0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders		10.9	31.6	18.1	120.7
Segment Reporting Information, Assets [Abstract]
Total assets		2,565.0		2,565.0		$ 2,387.5
Co-Investments | Rental | Operating Segments
Revenue
Total revenue		0.0	0.0	0.0	0.0
Expenses
Cost of goods and services		0.0	0.0	0.0	0.0
Co-Investments | Hotel | Operating Segments
Revenue
Total revenue		0.0	0.0	0.0	0.0
Expenses
Cost of goods and services		0.0	0.0	0.0	0.0
Co-Investments | Investment management fees | Operating Segments
Revenue
Total revenue		19.1	11.0	30.1	22.3
Co-Investments | Loans | Operating Segments
Revenue
Total revenue		4.7	2.7	8.4	5.0
Co-Investments | Compensation and related | Operating Segments
Expenses
Cost of goods and services		10.1	10.9	18.5	25.3
Co-Investments | Other Revenue | Operating Segments
Revenue
Total revenue		$ 0.0	$ 0.0	$ 0.0	$ 0.0
Minimum
Segment Reporting Information [Line Items]
Average ownership interest in investments		5.00%		5.00%
Maximum
Segment Reporting Information [Line Items]
Average ownership interest in investments		50.00%		50.00%

[1] The assets and liabilities as of June 30, 2023 include $157.4 million (including cash held by consolidated investments of $4.7 million and real estate and acquired in place lease values, net of accumulated depreciation and amortization of $123.3 million) and $77.0 million (including investment debt of $53.8 million), respectively, from consolidated variable interest entities ("VIEs"). The assets and liabilities as of December 31, 2022 include $169.8 million (including cash held by consolidated investments of $6.1 million and real estate and acquired in place lease values, net of accumulated depreciation and amortization of $137.8 million) and $82.4 million (including investment debt of $51.2 million), respectively, from VIEs. These assets can only be used to settle obligations of the consolidated VIEs, and the liabilities do not have recourse to the Company.