Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	9 Months Ended					3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Fair Value, Inputs, Level 2	Dec. 31, 2012 Fair Value, Inputs, Level 2	Sep. 30, 2013 Identified Intangible Assets	Sep. 30, 2012 Identified Intangible Assets	Sep. 30, 2013 Identified Intangible Assets	Sep. 30, 2012 Identified Intangible Assets
Significant Accounting Policies [Line Items]
Intangible assets and goodwill	$ 12,100,000		$ 12,100,000
Intangible assets	4,300,000		4,300,000
Goodwill	7,800,000		7,800,000
Accumulated amortization of identified intangible assets	1,800,000		1,500,000
Amortization expense for identified intangible assets	803,000	44,314,000				100,000	100,000	300,000	300,000
Cash and cash equivalents, restricted cash	5,200,000		4,900,000
Mortgage notes payable fair value				2,200,000,000	2,200,000,000
Accumulated amortization for deferred financing costs	$ 24,300,000		$ 20,500,000