Real Estate Activities - Dispositions of Assets for Discontinued Operations (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013
2010 Credit Facility [Member] \| January [Member] \| Mall [Member]
Disposals [Line Items]
Proceeds from the sale of property to repay	$ 11.5
Available working capital pay for release	4.5
2010 Credit Facility [Member] \| February [Member] \| Mall [Member]
Disposals [Line Items]
Proceeds from the sale of property to repay	35.0
Mortgage loans on real estate [Member] \| Power center [Member]
Disposals [Line Items]
Proceeds from the sale of property to repay	$ 50.0

Cash received for the sale of real estate that is not part of an investing activity during the current period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 24

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_ProceedsFromSaleOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration