Investments in Partnerships (Summary of Mortgage Loans Secured by Our Unconsolidated Properties) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Partnership Mortgage Loan Activity [Line Items]
Number Of Properties Securing Mortgage Debt	8
Gloucester Premium Outlets [Member]
Partnership Mortgage Loan Activity [Line Items]
Percentage Of Interest In Unconsolidated Entity	25.00%
Mortgages [Member] | Gloucester Premium Outlets [Member]
Partnership Mortgage Loan Activity [Line Items]
Amount Financed or Extended (in millions of dollars)	1.6
Mortgages [Member] | Maximum [Member] | Gloucester Premium Outlets [Member]
Partnership Mortgage Loan Activity [Line Items]
Amount Financed or Extended (in millions of dollars)	90.0
Debt Instrument, Unused Borrowing Capacity, Amount	88.4
Gloucester Premium Outlets [Member] | Construction Loan Payable [Member] | LIBOR [Member]
Partnership Mortgage Loan Activity [Line Items]
Property	Gloucester Premium Outlets
Stated Interest Rate	1.50%