Noncontrolling Interests (Redeemable Preferred Units) (Narrative) (Details) (USD $)		3 Months Ended	9 Months Ended									3 Months Ended		9 Months Ended					9 Months Ended
	Sep. 30, 2013 Noncontrolling Interests [Member]	Sep. 30, 2013 Series Two Preferred Units [Member]	Sep. 30, 2013 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Aug. 15, 2013 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	May 15, 2013 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	May 14, 2013 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Feb. 15, 2013 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Dec. 31, 2012 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Dec. 31, 2011 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Dec. 31, 2010 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Dec. 31, 2009 Series Two Preferred Units [Member] Noncontrolling Interests [Member]	Sep. 30, 2013 series four preferred units [Member]	Aug. 07, 2013 series four preferred units [Member]	Sep. 30, 2013 series four preferred units [Member] Noncontrolling Interests [Member]	Aug. 15, 2013 series four preferred units [Member] Noncontrolling Interests [Member]	May 29, 2013 series four preferred units [Member] Noncontrolling Interests [Member] D	May 15, 2013 series four preferred units [Member] Noncontrolling Interests [Member]	Feb. 15, 2013 series four preferred units [Member] Noncontrolling Interests [Member]	Sep. 30, 2013 Redemption Year Two Thousand Fourteen [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Maximum Redeemable On Redemption Dates Preferred Units																			1,007,662
Series Two Preferred Units (in shares)	995,997		995,997
Liquidation preference percentage			6.00%
Preferred Units Liquidation Preference		$ 50.00	$ 50.00									$ 50.00	$ 50.00	$ 50.00
First opportunity to redeem Series Four Preferred Units (in days)																30
Series Four Preferred Units Redeemed													861,400
Operating Units liquidation preference (in dollars per share)			$ 38.10
OP Units for each Preferred Unit (in shares)		1.312336	1.312336
Series Two Preferred Units Redemption Price																			$ 50.00
Dates Series Two Preferred Unit Holders Can Require Redemption From Operating Partnership																			May 12, 2014
Maximum portion that may be required for redemption of total																			0.1666666667
Distributions to Series Two Preferred Units (in dollars per share)				$ 0.85302	$ 0.85302		$ 0.85302								$ 0.25		$ 0.25	$ 0.25
Series Four Preferred Units (in shares)	360,126													360,126
Series Four Preferred Units Annual Dividend Payable Rate												2.00%		2.00%
Number Of Holders Exercises						0		0	0	0	0