Real Estate Activities - Dispositions of Assets for Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended
	Apr. 30, 2013	Jun. 30, 2013 2013 Activity [Member] January [Member] Mall [Member]	Jun. 30, 2013 2013 Activity [Member] January [Member] Power center [Member]	Jun. 30, 2013 2013 Activity [Member] February [Member] Mall [Member]
Disposals [Line Items]
Capitalization Rate	5.70%	9.80%	6.90%	9.80%
Sale Price (in millions of dollars)		$ 11.5	$ 76.8	$ 35.0
Gain (in millions of dollars)			$ 32.7	$ 0.6