Derivatives (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		5 Months Ended	12 Months Ended			1 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May 31, 2013
Derivative Instruments [Line Items]
Estimate increase to interest expense			$ 3.4	$ 3.4
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)				(1.8)	3.4	1.2
Interest expense, mark to market			0.5
Loss reclassified from Accumulated Other Comprehensive Income (Loss) into income (effective portion)				2.5
Derivative, interest expense						0.6
Fair value of derivatives in a net liability position			(2.4)	(2.4)
Termination value			(2.8)	(2.8)
Loss on Cash Flow Hedge Ineffectiveness	0.1	1.2
Jacksonville Mall [Member]
Derivative Instruments [Line Items]
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)							2.9
Logan Valley Mall [Member]
Derivative Instruments [Line Items]
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)				0.5
Accelerated amortization expense					0.5
Interest Expense [Member]
Derivative Instruments [Line Items]
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)				1.8	3.4	1.2
Loss reclassified from Accumulated Other Comprehensive Income (Loss) into income (effective portion)				4.3	9.9	18.8
Interest Expense [Member] | Jacksonville Mall [Member]
Derivative Instruments [Line Items]
Loss reclassified from Accumulated Other Comprehensive Income (Loss) into income (effective portion)					2.9
Interest rate swap [Member]
Derivative Instruments [Line Items]
Number of derivative, interest rate swap agreement			12	12
Derivative, Weighted average interest rate			1.67%	1.67%
Derivative, notional amount			327.7	327.7
Period of amortization				10 years
Interest rate swap [Member] | 2010 Credit Facility [Member]
Derivative Instruments [Line Items]
Number of derivative, interest rate swap agreement						3
Derivative, notional amount						40.0
Deferred losses in other comprehensive income						0.6
Swap expiration date						March 2013
Forward Starting Swap [Member]
Derivative Instruments [Line Items]
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)							2.9
Interest Rate Swap Twelve [Member]
Derivative Instruments [Line Items]
Derivative, Maturity Date				Jan. 01, 2019
Interest Rate Swap Eleven and Twelve [Member]
Derivative Instruments [Line Items]
Derivative Liability, Notional Amount, Ineffective			$ 40.0	$ 40.0