Financing Activity - Mortgage Loan Activity (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Mortgage Loan February [Member] | Francis Scott Key Mall [Member]
Mortgage Loan Activity [Line Items]
Amount Financed or Extended (in millions of dollars)	$ 62.6
Maturity	March 2018
Mortgage Loan February [Member] | Francis Scott Key Mall [Member] | London Interbank Offered Rate (LIBOR) [Member]
Mortgage Loan Activity [Line Items]
Stated Interest Rate	2.60%
Mortgage Loan February [Member] | Lycoming Mall [Member]
Mortgage Loan Activity [Line Items]
Amount Financed or Extended (in millions of dollars)	35.5
Maturity	March 2018
Mortgage Loan February [Member] | Lycoming Mall [Member] | London Interbank Offered Rate (LIBOR) [Member]
Mortgage Loan Activity [Line Items]
Stated Interest Rate	2.75%
Mortgage Loan February [Member] | Viewmont Mall [Member]
Mortgage Loan Activity [Line Items]
Amount Financed or Extended (in millions of dollars)	48.0
Maturity	March 2018
Mortgage Loan February [Member] | Viewmont Mall [Member] | London Interbank Offered Rate (LIBOR) [Member]
Mortgage Loan Activity [Line Items]
Stated Interest Rate	2.60%
Mortgage Loan March [Member] | Dartmouth Mall [Member]
Mortgage Loan Activity [Line Items]
Amount Financed or Extended (in millions of dollars)	$ 67.0
Stated Interest Rate	3.97%
Maturity	April 2018