Real Estate and In-Place Lease Value - Schedule of Acquisitions (Details) (USD $) In Millions, unless otherwise specified		6 Months Ended																				3 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Commercial Acquired in United Kingdom 1 [Member] Property		Jun. 30, 2014 Hotel Acquired in Western United States [Member] room	Jun. 30, 2014 Multifamily Acquired in Ireland [Member] Property apartment_unit sqft penthouse_unit	Jun. 30, 2014 Commercial Acquired in United Kingdom 2 [Member] Property		Jun. 30, 2014 Multifamily Acquired in Ireland 2 [Member] sqft apartment_unit acre		Jun. 30, 2014 Commercial Acquired in Western U.S. 1 [Member] sqft	Jun. 30, 2014 Multifamily Acquired in Western U.S. 1 [Member] Unit	Jun. 30, 2014 Multifamily Acquired in Ireland 3 [Member] Unit		Jun. 30, 2014 Commercial Acquired in Ireland 2 [Member] Property		Jun. 30, 2014 Commercial Acquired in United Kingdom 3 [Member] Property		Jun. 30, 2014 Multifamily Acquired in Western U.S. 2 [Member] Unit	Jun. 30, 2014 Commercial Acquired in Ireland [Member] Property	Jun. 30, 2014 Commercial and Loan Acquired in UK [Member] Property	Feb. 28, 2014 KWE [Member]	Jun. 30, 2014 KWE [Member] Commercial Acquired in United Kingdom 3 [Member]
Business Acquisition [Line Items]
Land	$ 377.4	$ 28.9	[1]	$ 1.3	$ 0.6	$ 54.0	[2]	$ 32.7	[3]	$ 2.4	$ 2.7	$ 4.8	[2]	$ 104.9	[2]	$ 106.8	[2],[4]	$ 38.3
Building	1,030.7	47.1	[1]	8.3	15.1	132.0	[2]	80.9	[3]	5.8	24.0	15.0	[2]	344.3	[2]	300.7	[2],[4]	57.5
Intangible assets	278.0	41.4	[1]	0	0.4	54.0	[2]	1.2	[3]	0.4	0.3	0.4	[2]	52.3	[2]	127.0	[2],[4]	0.6
Investment debt	458.1	0	[1]	0	9.6	0	[2]	78.9	[3]	6.0	13.3	0	[2]	273.1	[2]	0	[2],[4]	77.2
KWH Shareholders' Equity	274.5	58.7		6.9	6.5	29.3		35.9		1.9	13.3	2.7		30.1		70.6		18.6
Number of properties acquired		14			3	26								13		20			2	2
Number of rooms acquired				193
Number of apartment units acquired					24			281			203	81						542
Number of penthouse units acquired					2
Square feet of property acquired					1,000			725,000		98,000
Number of acres acquired								7.4
Contribution of interest percentage in portfolio																					50.00%
Acquisition related gain																						$ 15.2

[1] On February 28, 2014, the Company contributed its 50% interest in this portfolio to KWE as part of the Company's investment in KWE's initial public offering.

[2] These portfolios of properties were acquired by KWE.

[3] This asset was sold to KWE on June 24, 2014.

[4] KWE acquired subordinated notes on this property during the quarter and used its position as a debt holder to secure the transaction. The Company recognized an acquisition-related gain of $15.2 million on the transaction due to its ability to acquire the underlying real estate at a discount to its fair value.