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), Including Portion Attributable to Nonredeemable Noncontrolling Interest	14,156	0	0	0	0	12,413	12,413	1,743
Common stock issued pursuant to:
Stock Granted During Period, Value, Share-based Compensation, Net of Forfeitures	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	1,422	0	(86)	1,508	0	0	1,422	0
Distributions to noncontrolling interests	(1,700)	0	0	0	0	0	0	(1,700)
Preferred Stock Redemption	0
Cash preferred dividends paid	(9,680)	0	0	0	0	(9,680)	(9,680)	0
Cash common dividends paid	(14,064)	0	0	0	0	(14,064)	(14,064)	0
Ending Balance at Sep. 30, 2012	627,900	169,602	107,706	689,194	(86,840)	(285,508)	594,154	33,746
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), Including Portion Attributable to Nonredeemable Noncontrolling Interest	122,702	0	0	0	0		117,862	4,840
Common stock issued pursuant to:
Stock Granted During Period, Value, Share-based Compensation, Net of Forfeitures	544	0	50	494	0	0	544	0
Stock Issued During Period, Value, Stock Options Exercised	(137)	0	25	(162)	0	0	(137)	0
Stock Issued During Period, Value, New Issues	826,529	0	85,507	741,022	0	0	826,529	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	1,421	0	(42)	1,463	0	0	1,421	0
Distributions to noncontrolling interests	(25,888)	0	0	0	0	0	0	(25,888)
Preferred Stock Redemption	(74,827)	(74,827)	0	(10,822)	0	10,822	(74,827)	0
Cash preferred dividends paid	(8,231)	0	0	0	0	(8,231)	(8,231)	0
Cash common dividends paid	(18,657)	0	0	0	0	(18,657)	(18,657)	0
Ending Balance at Sep. 30, 2013	$ 1,465,230	$ 94,775	$ 193,230	$ 1,420,810	$ (86,840)	$ (158,308)	$ 1,463,667	$ 1,563