EQUITY - Accumulated Other Comprehensive Income (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	$ 2,865.1
Unrealized (losses) gains, arising during the period	(281.2)
Amounts reclassified out of AOCI during the period	3.4
Taxes on unrealized (losses) gains, arising during the period	17.1
Noncontrolling interest	237.2
Balance (of Kennedy Wilson's share) at December 31, 2016	2,343.1
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	(69.9)
Unrealized (losses) gains, arising during the period	(184.9)
Amounts reclassified out of AOCI during the period	3.8
Taxes on unrealized (losses) gains, arising during the period	20.8
Noncontrolling interest	131.6
Balance (of Kennedy Wilson's share) at December 31, 2016	(98.6)
Foreign Currency Derivative Contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	22.4
Unrealized (losses) gains, arising during the period	(96.4)
Amounts reclassified out of AOCI during the period	(0.4)
Taxes on unrealized (losses) gains, arising during the period	(3.7)
Noncontrolling interest	105.6
Balance (of Kennedy Wilson's share) at December 31, 2016	27.5
Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	(0.2)
Unrealized (losses) gains, arising during the period	0.1
Amounts reclassified out of AOCI during the period	0.0
Taxes on unrealized (losses) gains, arising during the period	0.0
Noncontrolling interest	0.0
Balance (of Kennedy Wilson's share) at December 31, 2016	(0.1)
Total Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	(47.7)
Balance (of Kennedy Wilson's share) at December 31, 2016	$ (71.2)