Real Estate and In-Place Lease Value - Schedule of Gains on Sale of Real Estate (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) property	Jun. 30, 2017 USD ($)
Gain on sale of real estate
Consolidated | $	$ 267.2	$ 75.0
KW [Member]
Gain on sale of real estate
Consolidated | $	230.0
NCI | $	69.0
Net of NCI | $	$ 161.0
Multifamily [Member] | KW [Member] | Ireland [Member]
Gain on sale of real estate
Number of real estate properties sold | property	3
Residential Property [Member] | KW [Member] | Western U.S. [Member]
Gain on sale of real estate
Number of real estate properties sold | property	1
Residential Property [Member] | KW [Member] | Ireland [Member]
Gain on sale of real estate
Number of real estate properties sold | property	1
Commercial [Member] | KW [Member] | United Kingdom [Member]
Gain on sale of real estate
Number of real estate properties sold | property	15