Financing Activity - Additional Information (Detail) (USD $)	3 Months Ended			3 Months Ended						1 Months Ended	3 Months Ended										3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Second Extension [Member]	Mar. 31, 2013 Term Loan [Member]	Mar. 31, 2012 Term Loan [Member]	Mar. 31, 2013 2010 Term Loan [Member]	Feb. 28, 2013 Moorestown [Member]	Mar. 31, 2013 Revolving Facility [Member]	Mar. 31, 2012 Revolving Facility [Member]	Mar. 31, 2013 2013 Revolving Credit Facility [Member]	Mar. 31, 2013 2013 Revolving Credit Facility [Member] LIBOR [Member] Minimum [Member]	Mar. 31, 2013 2013 Revolving Credit Facility [Member] LIBOR [Member] Maximum [Member]	Mar. 31, 2012 2013 Revolving Credit Facility [Member] Wells Fargo Bank [Member]	Mar. 31, 2013 2013 Revolving Credit Facility [Member] Wells Fargo Bank [Member]	Mar. 31, 2012 2013 Revolving Credit Facility [Member] Wells Fargo Bank [Member] Minimum [Member]	Mar. 31, 2013 EBITDA [Member] Minimum [Member]	Mar. 31, 2013 EBITDA [Member] Maximum [Member]	Mar. 31, 2013 Secured indebtedness [Member]	Mar. 31, 2013 Maximum Investments in unimproved real estate and predevelopment costs [Member]	Mar. 31, 2013 Maximum Investments in Persons other than Subsidiaries, Consolidated Affiliates and Unconsolidated Affiliates [Member]	Mar. 31, 2013 Maximum Investments in Indebtedness secured by Mortgages [Member]	Mar. 31, 2013 Aggregate value of the Investments [Member]	Mar. 31, 2013 Maximum Investments in Consolidation Exempt Entities [Member]	Mar. 31, 2013 Maximum Projects Under Development [Member]	Mar. 31, 2013 Aggregate of consolidation exempt entities and project [Member]
Debt Instrument [Line Items]
Revolving line of credit capacity											$ 250,000,000
Term loans	60,000,000						97,500,000
Revolving Facility outstanding											60,000,000
Revolving Facility pledged as collateral											0
Revolving Facility unused											190,000,000
Weighted average rate on Revolving Facility, outstanding											3.25%
Interest expense excluding non-cash amortization of finance costs	2,200,000	3,300,000									300,000	1,000,000
Weighted average interest rate of Term Loan							3.95%	5.08%						1.50%	2.05%
Non-cash amortization of deferred financing fees	900,000	700,000
Accelerated amortization of deferred financing fees	800,000
Permanent repayments of 2010 Term Loan							84,500,000
Senior Unsecured Credit Facility																	400,000,000
Outstanding commitments						0.20%
Maturity date													April 17, 2016
Effective initial interest rate													The initial rate in effect was 2.05% per annum in excess of LIBOR.
Capitalization rate used to calculate Gross Asset Value				6.50%	7.50%
Cost of property per square foot	500
Percentage of unused portion of the 2013 Revolving Facility													0.30%
Maximum amount available under revolving facility through accordion option																	600,000,000
Minimum increase to the Revolving Facility through accordion option																		25,000,000
Increments under accordion option																5,000,000
Minimum tangible net worth			75.00%
Net proceeds of equity issuances	75.00%
Ratio of Total Liabilities to Gross Asset Value	Maximum ratio of Total Liabilities to Gross Asset Value of 0.601, provided that it will not be a Default if the ratio exceeds 0.601 but does not exceed 0.6251, so long as the ratio does not exceed 0.601 for more than two consecutive quarters and such ratio has not exceeded 0.601 more than two times during the term;
Minimum ratio of Adjusted EBITDA to Fixed Charges																			1.45	1.50
Unencumbered Debt Yield	12.00%
Investment Percentage of Gross Asset Value	1.75
Maximum secured indebtedness																					0.60
Investment Percentage of Gross Asset Value																						5.00%	5.00%	5.00%	10.00%	25.00%	15.00%	35.00%
Percentage of distribution related to FFO	95.00%
REIT Taxable Income distributions	110.00%
Repayment of outstanding amount under revolving facility	84,500,000								97,500,000				95,000,000
Amount outstanding under revolving facility													192,500,000
Repayment of mortgage loans										53,200,000
Revolving Facility										50,000,000
Revolving Facility, working capital										$ 3,500,000