Unconsolidated Affiliates, Noncontrolling Interests and Cost Method Investments (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Dec. 31, 2009
Noncontrolling Interest [Line Items]
Minority Interest Decrease From Distributions To Redeemable Noncontrolling Interest Holders	$ (15,436)	$ (15,336)
Issuance Of Preferred Joint Venture Interest	0	2,146
Redeemable noncontrolling preferred joint venture interest	423,834	423,834	423,834	421,570
Number of entities - equity method of accounting	16
Non-controlling Interests [Abstract]
Total non-controlling interests	197,214		223,605
Total redeemable non-controlling partnership interests	24,507		34,379
Third Party Interests [Member]
Non-controlling Interests [Abstract]
Total non-controlling interests	190,827		217,519
Total redeemable non-controlling partnership interests	18,413		28,070
Consolidated Subsidiary [Member]
Non-controlling Interests [Abstract]
Total non-controlling interests	6,387		6,086
Total redeemable non-controlling partnership interests	$ 6,094		$ 6,309