Financing Activity - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended				1 Months Ended			3 Months Ended			9 Months Ended			3 Months Ended	9 Months Ended			9 Months Ended							1 Months Ended	3 Months Ended			9 Months Ended						9 Months Ended							3 Months Ended	9 Months Ended			9 Months Ended
	May 31, 2013	Sep. 30, 2013 Extension	Sep. 30, 2013 Extension	Sep. 30, 2012	May 02, 2013	Dec. 31, 2012	Feb. 28, 2013 Moorestown [Member]	May 31, 2013 Jacksonville [Member]	Apr. 30, 2013 2010 Term Loan [Member]	Sep. 30, 2013 2010 Term Loan [Member]	Mar. 31, 2013 2010 Term Loan [Member]	Sep. 30, 2012 2010 Term Loan [Member]	Sep. 30, 2013 2010 Term Loan [Member]	Sep. 30, 2012 2010 Term Loan [Member]	May 31, 2013 2013 Activity [Member] Jacksonville [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member]	Oct. 01, 2013 2013 Revolving Credit Facility [Member]	Apr. 17, 2013 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member] Minimum [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member] Minimum [Member] LIBOR [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member] Maximum [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member] Maximum [Member] LIBOR [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member] First Extension [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member] Second Extension [Member]	Apr. 17, 2013 2010 Credit Facility [Member]	Apr. 30, 2013 2010 Revolving Facility [Member]	Sep. 30, 2013 2010 Revolving Facility [Member]	Mar. 31, 2013 2010 Revolving Facility [Member]	Sep. 30, 2012 2010 Revolving Facility [Member]	Sep. 30, 2013 2010 Revolving Facility [Member]	Sep. 30, 2012 2010 Revolving Facility [Member]	Sep. 30, 2013 Secured indebtedness [Member] Minimum [Member]	Sep. 30, 2013 Secured indebtedness [Member] Maximum [Member]	Sep. 30, 2013 EBITDA [Member] Minimum [Member]	Sep. 30, 2013 EBITDA [Member] Maximum [Member]	Sep. 30, 2013 Maximum Investments in unimproved real estate and predevelopment costs [Member]	Sep. 30, 2013 Maximum Investments in Persons other than Subsidiaries, Consolidated Affiliates and Unconsolidated Affiliates [Member]	Sep. 30, 2013 Maximum Investments in Indebtedness secured by Mortgages [Member]	Sep. 30, 2013 Aggregate value of the Investments [Member]	Sep. 30, 2013 Maximum Investments in Consolidation Exempt Entities [Member]	Sep. 30, 2013 Maximum Projects Under Development [Member]	Sep. 30, 2013 Aggregate of consolidation exempt entities and project [Member]	Sep. 30, 2012 Line of Credit [Member]	Sep. 30, 2013 Line of Credit [Member]	Sep. 30, 2012 Line of Credit [Member]	Feb. 28, 2013 2010 Term Loan [Member] Moorestown [Member]	Sep. 30, 2013 Wells Fargo Bank [Member] 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 Wells Fargo Bank [Member] 2013 Revolving Credit Facility [Member] Minimum [Member]	Feb. 28, 2013 Lycoming Mall [Member]	Mar. 31, 2010 Lycoming Mall [Member]	Oct. 31, 2009 Lycoming Mall [Member]
Debt Instrument [Line Items]
Senior Unsecured Credit Facility																										$ 250,000,000.0																						$ 400,000,000.0
Amount outstanding		90,000,000	90,000,000		192,500,000											90,000,000	90,000,000	160,000,000
Unused portion of line of credit																310,000,000	310,000,000	0
Additional Loan Amount Drawn																		70,000,000																																2,100,000	2,500,000	5,000,000
Weighted average rate on revolving facility, outstanding																1.88%	1.88%
Interest expense excluding non-cash amortization of finance costs												4,000,000	2,400,000	11,200,000		600,000	1,300,000													700,000	400,000	2,200,000
Non-cash amortization of deferred financing fees																400,000	800,000																											900,000	800,000	2,700,000
Revolving Credit Facility Extension Options Available		2	2
Outstanding commitments																								0.15%	0.20%
Weighted average interest rate of Term Loan												4.89%									1.50%		2.05%
Stated Interest Rate																			1.70%
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																																																600,000,000.0
Increments under accordion option																																																5,000,000.0
Minimum increase to the Revolving Facility through accordion option																																																	25,000,000
Minimum tangible net worth																75.00%	75.00%
Net proceeds of equity issuances																	75.00%
Maximum secured indebtedness																																	0.60	0.625
Minimum ratio of Adjusted EBITDA to Fixed Charges																																			1.45	1.50
Unencumbered Debt Yield																12.00%	12.00%
Investment Percentage of Gross Asset Value																	1.75
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%	95.00%
REIT Taxable Income distributions																	110.00%
Repayment of outstanding amount under revolving facility			182,000,000							97,500,000																		95,000,000
Amount outstanding under revolving facility																192,500,000
Term loans																												97,500,000			97,500,000
Accelerated amortization of deferred financing fees									100,000		800,000																				900,000
Permanent repayments of 2010 Term Loan																											97,500,000		84,500,000
Repayment of mortgage loans		12,000,000					53,200,000	56,300,000
Revolving Facility Debt Used To Repay Mortgage Debt															35,000,000																																50,000,000
Available Cash From Working Capital Used To Repay Mortgage Debt							3,500,000	21,300,000
Derivative Instruments, Loss Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing	$ 3,400,000	$ 700,000		$ 0				$ 2,900,000