Consolidated Statement of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Distributions in Excess of Net Income [Member]	Non-controlling Interest [Member]	Subsidiary of Common Parent [Member]	Subsidiary of Common Parent [Member] Preferred Stock [Member]	Subsidiary of Common Parent [Member] Common Stock [Member]	Subsidiary of Common Parent [Member] Limited Partner [Member]	Subsidiary of Common Parent [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Subsidiary of Common Parent [Member] Non-controlling Interest [Member]	Subsidiary of Common Parent [Member] Stockholders' Equity, Total [Member]
Beginning Balance - Partnership at Dec. 31, 2013								$ 3,044,385	$ 447,683	$ 2,565,370	$ 20,158	$ 4,119	$ 7,055	$ 3,037,330
Beginning Balance - General Partner at Dec. 31, 2013	3,044,629	447,683	3,264	4,620,964	4,119	(2,062,787)	31,386
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	25,571					25,237	334	25,571	7,037	18,200	250		84	25,487
Other comprehensive income	(287)				(287)			(287)				(287)		(287)
Issuance of common shares	23,783		14	23,769
Capital contribution from the General Partner								23,783		23,783				23,783
Stock based compensation plan activity	4,025		7	4,563		(545)		4,025		4,025				4,025
Distributions to preferred shareholders/unitholders	(7,037)					(7,037)		(7,037)	(7,037)					(7,037)
Repurchase of preferred shares/units	(17,656)	(18,757)		618		483		(17,656)	(18,757)	1,101				(17,656)
Partners' Capital Account, Distributions								(56,342)		(55,596)	(746)			(56,342)
Distributions to common shareholders	(55,596)					(55,596)
Distributions to noncontrolling interests, net	(770)						(770)	(24)					(24)
Ending Balance - Partnership at Mar. 31, 2014								3,016,418	428,926	2,556,883	19,662	3,832	7,115	3,009,303
Ending Balance - General Partner at Mar. 31, 2014	$ 3,016,662	$ 428,926	$ 3,285	$ 4,649,914	$ 3,832	$ (2,100,245)	$ 30,950