Acquisition of Rental Property Schedule of Purchase Price Allocation (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Business Acquisition [Line Items]
Business Combination, Purchase Price Allocation, Land	$ 6,425
Business Acquisition, Purchase Price Allocation, Property	287,933
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	88,412
Business Acquisition, Purchase Price Allocation, Mortgage Fair Value Adjustments	(7,770)
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net	375,000
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	(7,635)
Business Combination, Consideration Transferred	367,365
Leases, Acquired-in-Place, Market Adjustment [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	4,897
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	7
Ground Leases, Market Adjustment [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	29,092
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	86.3
Leases, Acquired-in-Place [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	23,340
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	3.8
Tenant Relationships [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	27,876
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	9.9
Lease and Legal Costs [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	$ 3,207
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	2.8