Unconsolidated Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 JointVenture	Mar. 31, 2013	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 619.7		$ 786.1
Investments in joint ventures	584.5		751.4
Contributions to Acquire Interest in Joint Venture	9.9
Foreign currency exchange gain (loss)	0.2	(3.9)
Payments to acquire equity method investment	(71.1)
Proceeds from equity method investments	17.3
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Unfulfilled capital commitments	12.5
Unfulfilled capital commitments, number with unfulfilled capital commitments	4
Investments in loan pool participations	35.2		34.7
Performance Guarantee [Member] | Loans Payable [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Guarantor obligations, maximum exposure	62.6
Guarantor obligations, maximum exposure, percentage of property level debt	1.00%
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable interest entity, number of investments	5
Variable interest entity, carrying amount assets	184.9
Variable interest entity, maximum loss exposure	71.1
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	5.00%
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%
Europe [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, number of investments amended	6
KW Residential, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	67.9		68.8
Equity method investment, ownership percentage	41.00%
Number of properties in portfolio	50
Number of units in portfolio	2,400
Foreign currency exchange gain (loss)	(1.0)	(4.3)
Proceeds from equity method investments	$ 0.4	$ 13.5