Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 9.8	$ 13.1	$ 32.6	$ 31.3
Other comprehensive income (loss), net of tax:
Unrealized foreign currency translation gain (loss)	50.5	(1.1)	171.3	(61.7)
Unrealized gain on marketable securities	0.1	0.1	0.2	0.2
Amounts reclassified out of AOCI during the period	0.1	0.7	0.1	3.4
Unrealized currency derivative contracts loss	(11.5)	(35.6)	(44.3)	(125.0)
Total other comprehensive income (loss) for the period	39.2	(35.9)	127.3	(183.1)
Comprehensive income (loss)	49.0	(22.8)	159.9	(151.8)
Comprehensive (income) loss attributable to noncontrolling interests	(52.9)	15.7	(138.8)	127.8
Comprehensive (loss) income attributable to Kennedy-Wilson Holdings, Inc. common shareholders	$ (3.9)	$ (7.1)	$ 21.1	$ (24.0)