Significant Transactions - Disposition of Interests in Unconsolidated Real Estate (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Gain (Loss) on Disposition of Other Assets	$ 21.9us-gaap_GainLossOnSaleOfOtherAssets
Parent Company [Member]
Gain (Loss) on Disposition of Other Assets	$ 15.7

Amount of gain (loss) on sale or disposal of other assets.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Name:	us-gaap_GainLossOnSaleOfOtherAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration