(Common Units) (Narrative) (Details) (USD $)	0 Months Ended				12 Months Ended		9 Months Ended
	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 29, 2014	Dec. 31, 2014 Y	Dec. 31, 2013	Sep. 30, 2014	Dec. 08, 2014
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distributions Declared To OP And LTIP Units Per Unit								$ 0.65
Distributions Declared To OPP and MYLTIP Units Per Unit								$ 0.065
OP Units for redemption (in shares)					80,246	929,441
Redemption of OP units issued on conversion of Series Two Preferred Units (in shares)					3,734	432,914
Redemption of OP units issued on conversion of LTIP Units (in shares)					67,857	24,028
Outperformance Awards LTIP Units distribution as percentage of OP Unit distribution prior to measurement date					10.00%
Distributions made to OP and LTIP units per unit (in dollars per share)	$ 0.65	$ 0.65	$ 0.65	$ 0.65
Distribution paid to outperformance awards, OPP Units and MYLTIP Units (in dollars per share)	$ 0.065	$ 0.065	$ 0.065	$ 0.065
Restriction on redemption of OP Unit to Common Stock (in years)					1
Redemption of OP Unit equivalence to Common Stock (in shares)					1
Common units of operating partnership if converted value					$ 2,300,000,000
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards in LTIP Units (in shares)					394,590
MYLTIP 2013 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards in LTIP Units (in shares)					313,936
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Closing price of common stock (in dollars per share)					$ 128.69
Quarter 3 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date					Oct. 31, 2014
Quarter 3 2014 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution Made to Limited Partner, Date of Record					Sep. 30, 2014
Dividend payable date					Oct. 31, 2014
Quarter 4 2013 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date					Jan. 29, 2014
Quarter 4 2013 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution Made to Limited Partner, Date of Record							Dec. 31, 2013
Dividend payable date					Jan. 29, 2014
Quarter 1 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date					Apr. 30, 2014
Quarter 1 2014 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution Made to Limited Partner, Date of Record					Mar. 31, 2014
Dividend payable date					Apr. 30, 2014
Quarter 2 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date					Jul. 31, 2014
Quarter 2 2014 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution Made to Limited Partner, Date of Record					Jun. 30, 2014
Dividend payable date					Jul. 31, 2014
Quarter 4 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date					Jan. 28, 2015
Dividends Payable, Date Declared					Dec. 08, 2014
Quarter 4 2014 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution Made to Limited Partner, Date of Record					Dec. 31, 2014
Dividend payable date					Jan. 28, 2015
Dividends Payable, Date Declared					Dec. 08, 2014
special dividend [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distributions Declared To OP And LTIP Units Per Unit								$ 4.50
Distributions made to OP and LTIP units per unit (in dollars per share)				$ 2.25
OPP Units 2011 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accelerated Compensation Expenses Related To 2011 OPP Units					$ 1,200,000