Acquisitions, Dispositions, Leasing and Financing Activities - The Allocation of the Aggregate Purchase Price (Detail) (USD $)	Jun. 30, 2013	Jun. 01, 2012	Jan. 31, 2013 1515 Market Street [Member]	Jan. 31, 2013 Lease Intangibles [Member] 1515 Market Street [Member]	Jun. 30, 2013 Above Market Lease Intangibles [Member]	Jan. 31, 2013 Above Market Lease Intangibles [Member] 1515 Market Street [Member]	Jun. 30, 2013 Below Market Lease [Member]	Jan. 31, 2013 Below Market Lease [Member] 1515 Market Street [Member]
Finite-Lived Intangible Assets [Line Items]
Land			$ 18,627,000
Building			23,159,000
Other improvements			73,000
Tenant improvements			1,407,000
Above market lease intangibles	17,810,000			14,943,000	2,867,000	2,867,000	(620,000)	(620,000)
Net working capital acquired			1,132,000
Other liabilities			(1,299,000)
Long term liabilities assumed			(60,279,000)
Net assets acquired		$ 363,000	$ 10,000