Real Estate Activities (Dispositions of Assets for Discontinued Operations) (Parenthetical) (Detail) (USD $)	12 Months Ended			1 Months Ended			3 Months Ended		1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2013 Paxton Towne Centre [Member]	Sep. 30, 2013 Christiana Center [Member]	Jan. 31, 2013 Christiana Center [Member]	Sep. 30, 2013 Chambersburg Mall [Member]	Mar. 31, 2013 Power Center [Member] Mortgage Loans on Real Estate [Member]	Feb. 28, 2013 2010 Credit Facility [Member] Mall [Member]	Jan. 31, 2013 2010 Credit Facility [Member] Mall [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member]
Disposals [Line Items]
Proceeds from the sale of property to repay								$ 50,000,000	$ 35,000,000	$ 11,500,000
Available working capital pay for release										4,500,000
Divestitures of goodwill	1,494,000	0	0	700,000		800,000
Repay borrowings under revolving facility											35,000,000
Mortgage loans assumed by buyer					49,200,000
Impairment losses							$ 23,700,000