Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Jun. 30, 2012
Property, Plant and Equipment [Line Items]
Consolidation percentage if not wholly owned but controlled	Less than 100%
Percentage of occupancy for stabilization	90.00%
Period after completion of construction for commencement of depreciation	1 year
Estimated useful lives	40 years
Average lease term period	7 years
Depreciation commencement description	Depreciation commences at the earlier of stabilization (defined as 90% occupied) or one year after completion of construction.
Investment maturity period	Three months or less
Noncontrolling interests in real estate entities	100.00%	28.20%
Percentage of taxable income distribute	100.00%
Europe Private Capital Segment [Member]
Property, Plant and Equipment [Line Items]
Goodwill	25.3
Minimum [Member]
Property, Plant and Equipment [Line Items]
Rental income held by Trustee	3 months
Maximum [Member]
Property, Plant and Equipment [Line Items]
Rental income held by Trustee	6 months
Capital Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Capital Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years
Tenant Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Depreciable and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years
Operating Properties [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	30 years