Real Estate and In-Place Lease Value Real Estate and In-Place Lease Value - Joint Venture Consolidations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Real Estate Properties [Line Items]
Cash	$ 17.5
Real estate and acquired in-place lease values, net	667.4
Accounts receivable and other assets	14.1
Accounts payable, accrued expenses, and other liabilities	18.4
Mortgage loans	290.3
Noncontrolling interests	206.5
Acquisition related gain	80.5
Multifamily Acquired in Ireland [Member]
Real Estate Properties [Line Items]
Cash	3.6
Real estate and acquired in-place lease values, net	248.5
Accounts receivable and other assets	0.9
Accounts payable, accrued expenses, and other liabilities	5.4
Mortgage loans	114.3
Noncontrolling interests	66.6
Acquisition related gain	37.8
Number of properties acquired	3
Commercial Acquired in Ireland [Member]
Real Estate Properties [Line Items]
Cash	4.3
Real estate and acquired in-place lease values, net	223.9
Accounts receivable and other assets	7.6
Accounts payable, accrued expenses, and other liabilities	4.9
Mortgage loans	75.2
Noncontrolling interests	77.9
Acquisition related gain	32.2
Number of properties acquired	2
Commercial and Loan Acquired in UK [Member]
Real Estate Properties [Line Items]
Cash	9.6
Real estate and acquired in-place lease values, net	195.0
Accounts receivable and other assets	5.6
Accounts payable, accrued expenses, and other liabilities	8.1
Mortgage loans	100.8
Noncontrolling interests	62.0
Acquisition related gain	$ 10.5
Number of properties acquired	2