Unconsolidated Investments - Cash Distributions by Investment Type and Location (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Schedule of Equity Method Investments [Line Items]
Operating	$ 17.9
Investing	35.2	$ 33.9
Multifamily [Member]
Schedule of Equity Method Investments [Line Items]
Operating	13.5
Investing	22.5
Commercial [Member]
Schedule of Equity Method Investments [Line Items]
Operating	4.1
Investing	6.7
Loan Pools [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.7
Residential and Other [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.3
Investing	5.3
Western United States [Member]
Schedule of Equity Method Investments [Line Items]
Operating	17.8
Investing	34.5
Western United States [Member] | Multifamily [Member]
Schedule of Equity Method Investments [Line Items]
Operating	13.4
Investing	22.5
Western United States [Member] | Commercial [Member]
Schedule of Equity Method Investments [Line Items]
Operating	4.1
Investing	6.7
Western United States [Member] | Loan Pools [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.0
Western United States [Member] | Residential and Other [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.3
Investing	5.3
United Kingdom [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.7
United Kingdom [Member] | Multifamily [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.0
United Kingdom [Member] | Commercial [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.0
United Kingdom [Member] | Loan Pools [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.7
United Kingdom [Member] | Residential and Other [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.0
Japan [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.1
Investing	0.0
Japan [Member] | Multifamily [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.1
Investing	0.0
Japan [Member] | Commercial [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.0
Japan [Member] | Loan Pools [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	0.0
Japan [Member] | Residential and Other [Member]
Schedule of Equity Method Investments [Line Items]
Operating	0.0
Investing	$ 0.0