Condensed Consolidated Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Treasury Stock	Distributions in Excess of Net Income	Stockholders' Investment	Nonredeemable Noncontrolling Interests
Beginning Balance at Dec. 31, 2011	$ 637,395	$ 169,602	$ 107,272	$ 687,835	$ (86,840)	$ (274,177)	$ 603,692	$ 33,703
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	900	0	0	0	0	(257)	(257)	1,157
Common stock issued pursuant to:
Director stock grants	540	0	72	468	0	0	540	0
Restricted stock grants, net of amounts withheld for income taxes	(169)	0	448	(617)	0	0	(169)	0
Amortization of stock options and restricted stock, net of forfeitures	1,210	0	(7)	1,217	0	0	1,210	0
Distributions to noncontrolling interests	(1,152)	0	0	0	0	0	0	(1,152)
Preferred Stock Redemption	0
Cash preferred dividends paid	(6,454)	0	0	0	0	(6,454)	(6,454)	0
Cash common dividends paid	(9,373)	0	0	0	0	(9,373)	(9,373)	0
Ending Balance at Jun. 30, 2012	622,897	169,602	107,785	688,903	(86,840)	(290,261)	589,189	33,708
Beginning Balance at Dec. 31, 2012	642,953	169,602	107,660	690,024	(86,840)	(260,104)	620,342	22,611
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	57,673	0	0	0	0	56,703	56,703	970
Common stock issued pursuant to:
Director stock grants	544		50	494	0	0	544	0
Stock option exercises	(121)		22	(143)	0	0	(121)	0
Common stock offering, net of issuance costs	165,100	0	16,507	148,593	0	0	165,100	0
Restricted stock grants, net of amounts withheld for income taxes	(1,179)	0	30	(1,209)	0	0	(1,179)	0
Amortization of stock options and restricted stock, net of forfeitures	987	0	(11)	998	0	0	987	0
Distributions to noncontrolling interests	(942)	0	0	0	0	0	0	(942)
Preferred Stock Redemption	(74,827)	(74,827)	0	(12,980)	0	12,980	(74,827)	0
Cash preferred dividends paid	(6,454)	0	0	0	0	(6,454)	(6,454)	0
Cash common dividends paid	(10,120)	0	0	0	0	(10,120)	(10,120)	0
Ending Balance at Jun. 30, 2013	$ 773,614	$ 94,775	$ 124,258	$ 825,777	$ (86,840)	$ (206,995)	$ 750,975	$ 22,639