Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	6 Months Ended					3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Fair Value, Inputs, Level 2	Dec. 31, 2012 Fair Value, Inputs, Level 2	Jun. 30, 2013 Identified Intangible Assets	Jun. 30, 2012 Identified Intangible Assets	Jun. 30, 2013 Identified Intangible Assets	Jun. 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	1,700,000		1,500,000
Amortization expense for identified intangible assets	318,000	36,766,000				100,000	100,000	200,000	200,000
Cash and cash equivalents, restricted cash	5,200,000		4,900,000
Mortgage notes payable fair value				2,400,000,000	2,400,000,000
Accumulated amortization for deferred financing costs	$ 23,100,000		$ 20,500,000