Consolidated Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss on Derivative Instruments	Distributions in Excess of Net Income	Stockholders' Investment	Nonredeemable Noncontrolling Interests
Beginning Balance at Dec. 31, 2008	$ 504,262	$ 169,602	$ 54,922	$ 368,829	$ (86,840)	$ (16,601)	$ (23,189)	$ 466,723	$ 37,539
Net income	29,721						27,295	27,295	2,426
Other comprehensive income	7,084					7,084		7,084
Total comprehensive income (loss)	36,805					7,084	27,295	34,379	2,426
Common stock issued pursuant to:
Common stock offering, net of issuance costs	318,406		46,000	272,406				318,406
Stock dividend, net of issuance costs	0		2,420	17,291			(19,711)
Director stock grants	265		29	236				265
Amortization of stock options and restricted stock, net of forfeitures	3,478		(19)	3,497				3,478
Income tax deficiency from stock based compensation	(43)			(43)				(43)
Distributions to nonredeemable noncontrolling interests	(7,117)								(7,117)
Change in fair value of redeemable noncontrolling interests	(180)						(180)	(180)
Cash preferred dividends paid	(12,907)						(12,907)	(12,907)
Cash common dividends paid	(22,710)						(22,710)	(22,710)
Ending Balance at Dec. 31, 2009	820,259	169,602	103,352	662,216	(86,840)	(9,517)	(51,402)	787,411	32,848
Net income	(12,209)						(14,573)	(14,573)	2,364
Other comprehensive income	9,517					9,517		9,517
Total comprehensive income (loss)	(2,692)					9,517	(14,573)	(5,056)	2,364
Common stock issued pursuant to:
Stock dividend, net of issuance costs	(95)		3,353	20,834			(24,282)	(95)
Director stock grants	250		35	215				250
Restricted stock grants, net of amounts withheld for income taxes	(74)		256	(330)				(74)
Amortization of stock options and restricted stock, net of forfeitures	2,348		(34)	2,382				2,348
Distributions to nonredeemable noncontrolling interests	(2,440)								(2,440)
Change in fair value of redeemable noncontrolling interests	378			(766)			1,144	378
Cash preferred dividends paid	(12,907)						(12,907)	(12,907)
Cash common dividends paid	(12,176)						(12,176)	(12,176)
Ending Balance at Dec. 31, 2010	792,851	169,602	106,962	684,551	(86,840)		(114,196)	760,079	32,772
Net income	(124,900)						(128,425)	(128,425)	3,525
Other comprehensive income
Total comprehensive income (loss)	(124,900)						(128,425)	(128,425)	3,525
Common stock issued pursuant to:
Director stock grants	707		82	625				707
Stock option exercises	18		4	14				18
Restricted stock grants, net of amounts withheld for income taxes	(9)		243	(252)				(9)
Amortization of stock options and restricted stock, net of forfeitures	2,112		(19)	2,131				2,112
Contributions from nonredeemable noncontrolling interests	1,300								1,300
Distributions to nonredeemable noncontrolling interests	(3,894)								(3,894)
Change in fair value of redeemable noncontrolling interests	766			766				766
Cash preferred dividends paid	(12,907)						(12,907)	(12,907)
Cash common dividends paid	(18,649)						(18,649)	(18,649)
Ending Balance at Dec. 31, 2011	$ 637,395	$ 169,602	$ 107,272	$ 687,835	$ (86,480)		$ (274,177)	$ 603,692	$ 33,703