Equity and Capital - Noncontrolling Interest of Limited Partners (Details) (USD $)	0 Months Ended	12 Months Ended
	Feb. 09, 2012	Dec. 31, 2012	Dec. 31, 2011
Limited Partners' Capital Account [Line Items]
Limited Partners' Capital Account, Units Outstanding		177,164	177,164
Series D Preferred Units, Number Outstanding			500,000
Distributions Paid To Preferred Unit Holders	$ 1,000,000
Partners' Capital Account, Units		90,571,650	90,099,022
General Partners' Capital Account, Units Outstanding		90,394,486	89,921,858
Noncontrolling Interest in Operating Partnerships		16,300,000	13,100,000
Series D preferred units, par value			$ 50,000,000
Distribution rate	3.75%		7.45%
Preferred Stock, Callable Date		Sep. 29, 2009
Preferred Unit, Exchangeable Date		Jan. 01, 2014
Parent Company [Member]
Limited Partners' Capital Account [Line Items]
Parent Company, Ownership Percentage of Outstanding Common Partnership Units of Operating Partnership		99.80%	99.80%