Noncontrolling Interests (Redeemable Preferred Units) (Narrative) (Details) (USD $)	9 Months Ended
	Sep. 30, 2011	Aug. 15, 2011	May 16, 2011	May 12, 2011	Feb. 15, 2011	May 12, 2010	May 12, 2009
Noncontrolling Interests [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Series Two Preferred Units	1,113,044
Noncontrolling Interests [Member] | Series Two Preferred Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Series Two Preferred Units	1,113,044
Liquidation preference percentage	6.00%
Preferred Units liquidation preference	$ 50.00
Operating Units liquidation preference	$ 38.10
OP Units for each Preferred Unit	1.312336
Distributions to Series Two Preferred Units		0.75616	0.73151		0.75616
Number of holders exercising redemption rights				0		0	0
Redemption Year Two Thousand Twelve [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Maximum redeemable Preferred Units	1,007,662
Dates Series Two Preferred holders can require Operating Partnership to redeem their units for cash	May 14, 2012
Series Two Preferred Units redemption price per unit	$ 50
Maximum portion that may be required for redemption of total	0.166666666667
Redemption Year Two Thousand Thirteen [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Maximum redeemable Preferred Units	1,007,662
Dates Series Two Preferred holders can require Operating Partnership to redeem their units for cash	May 14, 2013
Series Two Preferred Units redemption price per unit	50
Maximum portion that may be required for redemption of total	0.166666666667
Redemption Year Two Thousand Fourteen [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Maximum redeemable Preferred Units	1,007,662
Dates Series Two Preferred holders can require Operating Partnership to redeem their units for cash	May 12, 2014
Series Two Preferred Units redemption price per unit	$ 50
Maximum portion that may be required for redemption of total	0.166666666667