Unaudited Pro Forma Consolidated Results of Operations (Parenthetical) (Detail) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Business Acquisition, Pro Forma Information [Line Items]
Property management expenses	$ 38,460	$ 35,076	$ 32,639
General and administrative expenses	26,744	23,833	22,559
Amortization of in-place leases	45,122	28,479	0
Anti-dilutive securities excluded from the computation of Earning per Common Share		4.6
Business Acquisition Pro Forma Information \| Scenario, Forecast
Business Acquisition, Pro Forma Information [Line Items]
Amortization of in-place leases		$ 73,600

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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