Guarantor and Non-Guarantor Financial Statements - Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Condensed Financial Statements, Captions [Line Items]
Total revenue	$ 146.5	$ 136.1	$ 278.7	$ 260.8
Total (loss) income from unconsolidated subsidiaries	(1.4)	30.7	4.3	136.1
Gain on sale of real estate, net	89.0	11.9	108.2	13.8
Total expenses	133.1	128.5	257.6	267.6
Income from consolidated subsidiaries	0.0	0.0	0.0	0.0
Interest expense	(66.0)	(53.2)	(128.3)	(103.7)
Loss on early extinguishment of debt	(1.7)	(1.1)	(1.6)	(1.1)
Other income	24.3	3.6	21.3	9.4
Income (loss) before provision for income taxes	57.6	(0.5)	25.0	47.7
Benefit from (provision for) income taxes	(10.3)	(0.4)	(6.4)	(8.6)
Net income (loss)	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
Rental
Condensed Financial Statements, Captions [Line Items]
Total revenue	106.6	109.3	213.2	213.5
Hotel
Condensed Financial Statements, Captions [Line Items]
Total revenue	15.5	12.7	26.1	19.2
Investment management fees
Condensed Financial Statements, Captions [Line Items]
Total revenue	19.1	11.0	30.1	22.3
Loan
Condensed Financial Statements, Captions [Line Items]
Total revenue	4.7	2.7	8.4	5.0
Reportable Legal Entities | Parent
Condensed Financial Statements, Captions [Line Items]
Total revenue	0.0	0.0	0.0	0.0
Total (loss) income from unconsolidated subsidiaries	0.0	0.0	0.0	0.0
Gain on sale of real estate, net	0.0	0.0	0.0	0.0
Total expenses	7.3	7.4	14.9	14.5
Income from consolidated subsidiaries	54.5	6.4	33.3	53.5
Interest expense	0.0	0.0	0.0	0.0
Loss on early extinguishment of debt	0.0	0.0	0.0	0.0
Other income	0.1	0.0	0.2	0.0
Income (loss) before provision for income taxes	47.3	(1.0)	18.6	39.0
Benefit from (provision for) income taxes	0.0	0.0	0.0	0.0
Net income (loss)	47.3	(1.0)	18.6	39.0
Net loss (income) attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Preferred dividends	(8.4)	(7.8)	(16.3)	(13.1)
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	38.9	(8.8)	2.3	25.9
Reportable Legal Entities | Kennedy-Wilson, Inc.
Condensed Financial Statements, Captions [Line Items]
Total revenue	0.0	0.1	0.1	0.1
Total (loss) income from unconsolidated subsidiaries	(0.1)	(1.3)	(0.1)	0.7
Gain on sale of real estate, net	0.0	0.0	0.0	0.0
Total expenses	25.0	21.9	42.0	44.4
Income from consolidated subsidiaries	97.4	42.9	114.7	135.7
Interest expense	(24.9)	(22.3)	(50.1)	(44.0)
Loss on early extinguishment of debt	0.0	0.0	0.0	0.0
Other income	11.3	0.9	9.2	3.7
Income (loss) before provision for income taxes	58.7	(1.6)	31.8	51.8
Benefit from (provision for) income taxes	(4.2)	8.1	1.5	1.8
Net income (loss)	54.5	6.5	33.3	53.6
Net loss (income) attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Preferred dividends	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	54.5	6.5	33.3	53.6
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Total revenue	63.7	55.7	120.1	109.5
Total (loss) income from unconsolidated subsidiaries	(19.1)	5.5	(46.0)	14.0
Gain on sale of real estate, net	94.5	11.4	98.2	11.4
Total expenses	42.2	45.3	86.2	98.1
Income from consolidated subsidiaries	15.0	31.4	52.5	127.4
Interest expense	(12.6)	(10.4)	(23.4)	(20.1)
Loss on early extinguishment of debt	(1.5)	(1.1)	(2.0)	(1.1)
Other income	(0.2)	(0.4)	0.7	(0.7)
Income (loss) before provision for income taxes	97.6	46.8	113.9	142.3
Benefit from (provision for) income taxes	(0.2)	(3.9)	0.8	(6.6)
Net income (loss)	97.4	42.9	114.7	135.7
Net loss (income) attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Preferred dividends	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	97.4	42.9	114.7	135.7
Reportable Legal Entities | Non-guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Total revenue	82.8	80.3	158.5	151.2
Total (loss) income from unconsolidated subsidiaries	17.8	26.5	50.4	121.4
Gain on sale of real estate, net	(5.5)	0.5	10.0	2.4
Total expenses	58.6	53.9	114.5	110.6
Income from consolidated subsidiaries	0.0	0.0	0.0	0.0
Interest expense	(28.5)	(20.5)	(54.8)	(39.6)
Loss on early extinguishment of debt	(0.2)	0.0	0.4	0.0
Other income	13.1	3.1	11.2	6.4
Income (loss) before provision for income taxes	20.9	36.0	61.2	131.2
Benefit from (provision for) income taxes	(5.9)	(4.6)	(8.7)	(3.8)
Net income (loss)	15.0	31.4	52.5	127.4
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	15.1	31.1	48.4	127.2
Elimination
Condensed Financial Statements, Captions [Line Items]
Total revenue	0.0	0.0	0.0	0.0
Total (loss) income from unconsolidated subsidiaries	0.0	0.0	0.0	0.0
Gain on sale of real estate, net	0.0	0.0	0.0	0.0
Total expenses	0.0	0.0	0.0	0.0
Income from consolidated subsidiaries	(166.9)	(80.7)	(200.5)	(316.6)
Interest expense	0.0	0.0	0.0	0.0
Loss on early extinguishment of debt	0.0	0.0	0.0	0.0
Other income	0.0	0.0	0.0	0.0
Income (loss) before provision for income taxes	(166.9)	(80.7)	(200.5)	(316.6)
Benefit from (provision for) income taxes	0.0	0.0	0.0	0.0
Net income (loss)	(166.9)	(80.7)	(200.5)	(316.6)
Net loss (income) attributable to the noncontrolling interests	0.0	0.0	0.0	0.0
Preferred dividends	0.0	0.0	0.0	0.0
Net income (loss) attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ (166.9)	$ (80.7)	$ (200.5)	$ (316.6)