Guarantor and Non-Guarantor Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents		$ 665.6	$ 573.9
Accounts receivable		47.6	52.1
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		4,715.8	5,080.2
Unconsolidated investments		1,256.4	1,334.6
Investments in and advances to consolidated subsidiaries		0.0	0.0
Other assets, net		262.6	263.7
Total assets	[1]	6,948.0	7,304.5
Liabilities
Accounts payable		10.9	20.4
Accrued expenses and other liabilities		485.2	518.0
Total liabilities	[1]	5,293.0	5,585.3
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,612.5	1,678.7
Noncontrolling interests		42.5	40.5
Total equity		1,655.0	1,719.2	$ 1,302.2	$ 1,431.2
Total liabilities and equity		6,948.0	7,304.5
Mortgage Debt [Member]
Liabilities
Long-term debt		2,450.9	2,641.0
KW Unsecured Debt [Member]
Liabilities
Long-term debt		1,128.6	1,131.7
KWE Unsecured Bonds [Member]
Liabilities
Long-term debt		1,217.4	1,274.2
Reportable Legal Entities [Member] | Parent [Member]
Assets
Cash and cash equivalents		0.0	30.8
Accounts receivable		0.0	0.0
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		0.0	0.0
Unconsolidated investments		0.0	0.0
Investments in and advances to consolidated subsidiaries		1,648.1	1,682.3
Other assets, net		0.0	0.0
Total assets		1,648.1	1,713.1
Liabilities
Accounts payable		0.0	0.0
Accrued expenses and other liabilities		35.6	34.4
Total liabilities		35.6	34.4
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,612.5	1,678.7
Noncontrolling interests		0.0	0.0
Total equity		1,612.5	1,678.7
Total liabilities and equity		1,648.1	1,713.1
Reportable Legal Entities [Member] | Parent [Member] | Mortgage Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Parent [Member] | KW Unsecured Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Parent [Member] | KWE Unsecured Bonds [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Assets
Cash and cash equivalents		45.8	6.4
Accounts receivable		0.0	0.0
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		0.0	0.0
Unconsolidated investments		13.4	18.2
Investments in and advances to consolidated subsidiaries		2,918.6	3,037.5
Other assets, net		8.9	0.0
Total assets		2,986.7	3,062.1
Liabilities
Accounts payable		0.5	0.9
Accrued expenses and other liabilities		209.5	247.2
Total liabilities		1,338.6	1,379.8
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,648.1	1,682.3
Noncontrolling interests		0.0	0.0
Total equity		1,648.1	1,682.3
Total liabilities and equity		2,986.7	3,062.1
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | Mortgage Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | KW Unsecured Debt [Member]
Liabilities
Long-term debt		1,128.6	1,131.7
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member] | KWE Unsecured Bonds [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		91.4	102.7
Accounts receivable		12.9	13.9
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		2,064.3	2,052.3
Unconsolidated investments		473.9	526.0
Investments in and advances to consolidated subsidiaries		1,550.7	1,660.5
Other assets, net		64.8	61.1
Total assets		4,258.0	4,416.5
Liabilities
Accounts payable		2.0	3.4
Accrued expenses and other liabilities		62.2	59.7
Total liabilities		1,339.4	1,379.0
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		2,918.6	3,037.5
Noncontrolling interests		0.0	0.0
Total equity		2,918.6	3,037.5
Total liabilities and equity		4,258.0	4,416.5
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Mortgage Debt [Member]
Liabilities
Long-term debt		1,275.2	1,315.9
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | KW Unsecured Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | KWE Unsecured Bonds [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		528.4	434.0
Accounts receivable		34.7	38.2
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		2,651.5	3,027.9
Unconsolidated investments		769.1	790.4
Investments in and advances to consolidated subsidiaries		0.0	0.0
Other assets, net		188.9	202.6
Total assets		4,172.6	4,493.1
Liabilities
Accounts payable		8.4	16.1
Accrued expenses and other liabilities		177.9	176.7
Total liabilities		2,579.4	2,792.1
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,550.7	1,660.5
Noncontrolling interests		42.5	40.5
Total equity		1,593.2	1,701.0
Total liabilities and equity		4,172.6	4,493.1
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | Mortgage Debt [Member]
Liabilities
Long-term debt		1,175.7	1,325.1
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | KW Unsecured Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member] | KWE Unsecured Bonds [Member]
Liabilities
Long-term debt		1,217.4	1,274.2
Elimination [Member]
Assets
Cash and cash equivalents		0.0	0.0
Accounts receivable		0.0	0.0
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		0.0	0.0
Unconsolidated investments		0.0	0.0
Investments in and advances to consolidated subsidiaries		(6,117.4)	(6,380.3)
Other assets, net		0.0	0.0
Total assets		(6,117.4)	(6,380.3)
Liabilities
Accounts payable		0.0	0.0
Accrued expenses and other liabilities		0.0	0.0
Total liabilities		0.0	0.0
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		(6,117.4)	(6,380.3)
Noncontrolling interests		0.0	0.0
Total equity		(6,117.4)	(6,380.3)
Total liabilities and equity		(6,117.4)	(6,380.3)
Elimination [Member] | Mortgage Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Elimination [Member] | KW Unsecured Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Elimination [Member] | KWE Unsecured Bonds [Member]
Liabilities
Long-term debt		$ 0.0	$ 0.0

[1] The assets and liabilities as of March 31, 2020 include $136.3 million (including cash held by consolidated investments of $4.5 million and real estate and acquired in place lease values, net of accumulated depreciation and amortization of $122.9 million) and $84.4 million (including investment debt of $78.6 million), respectively, from consolidated variable interest entities ("VIEs"). The assets and liabilities as of December 31, 2019 include $267.5 million (including cash held by consolidated investments of $10.3 million and real estate and acquired in place lease values, net of accumulated depreciation and amortization of $243.5 million) and $219.7 million (including investment debt of $206.0 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.