Condensed Consolidated Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss on Derivative Instruments [Member]	Distributions in Excess of Net Income [Member]	Stockholders' Investment [Member]	Nonredeemable Noncontrolling Interests [Member]
Beginning balance at Dec. 31, 2009	$ 820,259	$ 169,602	$ 103,352	$ 662,216	$ (86,840)	$ (9,517)	$ (51,402)	$ 787,411	$ 32,848
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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)							0	(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)	0	(114,196)	760,079	32,772
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(124,900)						(128,425)	(128,425)	3,525
Common stock issued pursuant to:
Stock dividend, net of issuance costs							0
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
Distributions to nonredeemable noncontrolling interests	(3,894)								(3,894)
Contributions from nonredeemable noncontrolling interests	1,300								1,300
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	(86,840)	0	(274,177)	603,692	33,703
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	49,922						45,728	45,728	4,194
Common stock issued pursuant to:
Stock dividend, net of issuance costs							0
Director stock grants	540		72	468				540
Restricted stock grants, net of amounts withheld for income taxes	(207)		452	(659)				(207)
Amortization of stock options and restricted stock, net of forfeitures	2,244		(136)	2,380				2,244
Distributions to nonredeemable noncontrolling interests	(15,286)								(15,286)
Change in fair value of redeemable noncontrolling interests	0
Cash preferred dividends paid	12,907						(12,907)	(12,907)
Cash common dividends paid	18,748						(18,748)	(18,748)
Ending balance at Dec. 31, 2012	$ 642,953	$ 169,602	$ 107,660	$ 690,024	$ (86,840)	$ 0	$ (260,104)	$ 620,342	$ 22,611