Changes to Accrued Cease-Use Liability (Detail) (USD $)	1 Months Ended	3 Months Ended				9 Months Ended
	Dec. 31, 2010	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Real Estate Properties [Line Items]
Beginning balance		$ 2,463,000		$ 7,708,000		$ 2,592,000		$ 9,965,000
Accrued cease use costs				63,000				239,000
Impact of cease-use charges		135,000		(87,000)		135,000		89,000
Change in estimate				(427,000)				(427,000)
Payments		(64,000)		(729,000)		(193,000)		(3,162,000)
Ending balance		2,549,000		6,939,000		2,549,000		6,939,000
Sublease
Real Estate Properties [Line Items]
Impact of cease-use charges	2,500,000	150,000	[1]	324,000	[1]	150,000	[1]	324,000	[1]
Ending balance		$ 2,500,000		$ 2,600,000		$ 2,500,000		$ 2,600,000

[1] Total cease-use expense was offset by the related adjustment to deferred rent of approximately $15,000 during 2012 and $47,000 during 2011.