Guarantor and Non-Guarantor Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents		$ 569.2	$ 260.2
Cash held by consolidated investments		695.6	625.5
Accounts receivable		93.4	71.3
Loan purchases and originations		87.2	87.7
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		6,062.1	5,814.2
Unconsolidated investments		499.0	555.6
Investments in and advances to consolidated subsidiaries		0.0	0.0
Other assets		277.8	244.6
Total assets	[1]	8,284.3	7,659.1
Liabilities
Accounts payable		20.8	11.2
Accrued expenses and other liabilities		431.4	412.1
Total liabilities	[1]	5,932.6	5,316.0
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,027.5	1,048.0
Noncontrolling interests		1,324.2	1,295.1
Total equity		2,351.7	2,343.1
Total liabilities and equity		8,284.3	7,659.1
Investment Debt [Member]
Liabilities
Long-term debt		4,192.8	3,956.1
Senior Notes [Member]
Liabilities
Long-term debt		937.6	936.6
Line of Credit [Member]
Liabilities
Long-term debt		350.0
Reportable Legal Entities [Member] | Parent [Member]
Assets
Cash and cash equivalents		0.0	0.0
Cash held by consolidated investments		0.0	0.0
Accounts receivable		0.0	0.0
Loan purchases and originations		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		1,046.9	1,063.8
Other assets		0.0	0.0
Total assets		1,046.9	1,063.8
Liabilities
Accounts payable		0.0	0.0
Accrued expenses and other liabilities		19.4	15.8
Total liabilities		19.4	15.8
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,027.5	1,048.0
Noncontrolling interests		0.0	0.0
Total equity		1,027.5	1,048.0
Total liabilities and equity		1,046.9	1,063.8
Reportable Legal Entities [Member] | Kennedy-Wilson, Inc. [Member]
Assets
Cash and cash equivalents		410.4	106.0
Cash held by consolidated investments		0.0	0.0
Accounts receivable		0.1	0.0
Loan purchases and originations		0.3	0.3
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		0.0	0.0
Unconsolidated investments		19.5	18.8
Investments in and advances to consolidated subsidiaries		1,936.3	2,073.2
Other assets		1.9	2.6
Total assets		2,368.5	2,200.9
Liabilities
Accounts payable		0.2	0.5
Accrued expenses and other liabilities		33.8	200.0
Total liabilities		1,321.6	1,137.1
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,046.9	1,063.8
Noncontrolling interests		0.0	0.0
Total equity		1,046.9	1,063.8
Total liabilities and equity		2,368.5	2,200.9
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		45.6	45.4
Cash held by consolidated investments		0.0	0.0
Accounts receivable		47.9	37.5
Loan purchases and originations		5.7	12.1
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		1,456.2	1,482.5
Unconsolidated investments		314.4	380.0
Investments in and advances to consolidated subsidiaries		1,138.4	1,171.6
Other assets		44.1	39.7
Total assets		3,052.3	3,168.8
Liabilities
Accounts payable		1.6	1.6
Accrued expenses and other liabilities		135.5	157.2
Total liabilities		1,116.0	1,095.6
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,936.3	2,073.2
Noncontrolling interests		0.0	0.0
Total equity		1,936.3	2,073.2
Total liabilities and equity		3,052.3	3,168.8
Reportable Legal Entities [Member] | Non-guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		113.2	108.8
Cash held by consolidated investments		695.6	625.5
Accounts receivable		45.4	33.8
Loan purchases and originations		81.2	75.3
Real estate and acquired in place lease values, net of accumulated depreciation and amortization		4,605.9	4,331.7
Unconsolidated investments		165.1	156.8
Investments in and advances to consolidated subsidiaries		0.0	0.0
Other assets		231.8	202.3
Total assets		5,938.2	5,534.2
Liabilities
Accounts payable		19.0	9.1
Accrued expenses and other liabilities		242.7	39.1
Total liabilities		3,475.6	3,067.5
Equity
Kennedy-Wilson Holdings, Inc. shareholders' equity		1,138.4	1,171.6
Noncontrolling interests		1,324.2	1,295.1
Total equity		2,462.6	2,466.7
Total liabilities and equity		5,938.2	5,534.2
Reportable Legal Entities [Member] | Investment Debt [Member] | Parent [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Investment Debt [Member] | Kennedy-Wilson, Inc. [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Investment Debt [Member] | Guarantor Subsidiaries [Member]
Liabilities
Long-term debt		978.9	936.8
Reportable Legal Entities [Member] | Investment Debt [Member] | Non-guarantor Subsidiaries [Member]
Liabilities
Long-term debt		3,213.9	3,019.3
Reportable Legal Entities [Member] | Senior Notes [Member] | Parent [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Senior Notes [Member] | Kennedy-Wilson, Inc. [Member]
Liabilities
Long-term debt		937.6	936.6
Reportable Legal Entities [Member] | Senior Notes [Member] | Guarantor Subsidiaries [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Senior Notes [Member] | Non-guarantor Subsidiaries [Member]
Liabilities
Long-term debt		0.0	0.0
Reportable Legal Entities [Member] | Line of Credit [Member] | Parent [Member]
Liabilities
Long-term debt		0.0
Reportable Legal Entities [Member] | Line of Credit [Member] | Kennedy-Wilson, Inc. [Member]
Liabilities
Long-term debt		350.0
Reportable Legal Entities [Member] | Line of Credit [Member] | Guarantor Subsidiaries [Member]
Liabilities
Long-term debt		0.0
Reportable Legal Entities [Member] | Line of Credit [Member] | Non-guarantor Subsidiaries [Member]
Liabilities
Long-term debt		0.0
Elimination [Member]
Assets
Cash and cash equivalents		0.0	0.0
Cash held by consolidated investments		0.0	0.0
Accounts receivable		0.0	0.0
Loan purchases and originations		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		(4,121.6)	(4,308.6)
Other assets		0.0	0.0
Total assets		(4,121.6)	(4,308.6)
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		(4,121.6)	(4,308.6)
Noncontrolling interests		0.0	0.0
Total equity		(4,121.6)	(4,308.6)
Total liabilities and equity		(4,121.6)	(4,308.6)
Elimination [Member] | Investment Debt [Member]
Liabilities
Long-term debt		0.0	0.0
Elimination [Member] | Senior Notes [Member]
Liabilities
Long-term debt		0.0	$ 0.0
Elimination [Member] | Line of Credit [Member]
Liabilities
Long-term debt		$ 0.0

[1] The assets and liabilities as of June 30, 2017 include $4.8 billion (including cash held by consolidated investments of $0.6 billion and real estate and acquired in place lease values, net of accumulated depreciation and amortization of $3.8 billion) and $2.9 billion (including investment debt of $2.6 billion), respectively, from consolidated variable interest entities ("VIEs"). The assets and liabilities as of December 31, 2016 include $4.5 billion (including cash held by consolidated investments of $0.6 billion and real estate and acquired in place lease values, net of accumulated depreciation and amortization of $3.6 billion) and $2.7 billion (including investment debt of $2.4 billion), 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.