Condensed Consolidated Statements of Equity - USD ($) $ in Thousands	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, 2013	$ 1,458,972	$ 94,775	$ 193,236	$ 1,420,951	$ (86,840)	$ (164,721)	$ 1,457,401	$ 1,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	29,160	0	0	0	0	28,784	28,784	376
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	653	0	55	598	0	0	653	0
Stock Issued During Period, Value, Stock Options Exercised	(227)	0	40	(267)	0	0	(227)	0
Stock Issued During Period, Value, New Issues	321,912	0	26,700	295,212	0	0	321,912	0
Restricted stock grants, net of amounts withheld for income taxes	(925)	0	53	(978)	0	0	(925)	0
Amortization of stock options and restricted stock, net of forfeitures	1,508	0	(5)	1,513	0	0	1,508	0
Distributions to noncontrolling interests	(369)	0	0	0	0	0	0	(369)
Preferred Stock Redemption	(94,775)	(94,775)	0	3,530	0	(3,530)	(94,775)	0
Preferred dividends paid	(2,955)	0	0	0	0	(2,955)	(2,955)	0
Common dividends paid	(45,351)	0	0	0	0	(45,351)	(45,351)	0
Ending Balance at Sep. 30, 2014	1,667,603	0	220,079	1,720,559	(86,840)	(187,773)	1,666,025	1,578
Beginning Balance at Dec. 31, 2014	1,673,458	0	220,083	1,720,972	(86,840)	(180,757)	1,673,458	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	68,774	0	0	0	0		68,774	0
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	765	0	79	686	0	0	765	0
Stock Issued During Period, Value, Stock Options Exercised	(15)	0	4	(19)	0	0	(15)	0
Stock Issued During Period, Value, New Issues	24			24
Restricted stock grants, net of amounts withheld for income taxes	(821)	0	90	(911)	0	0	(821)	0
Amortization of stock options and restricted stock, net of forfeitures	1,104	0	0	1,104	0	0	1,104	0
Preferred Stock Redemption	0
Common dividends paid	(52,011)	0	0	0	0	(52,011)	(52,011)	0
Ending Balance at Sep. 30, 2015	$ 1,672,587	$ 0	$ 220,256	$ 1,721,856	$ (105,531)	$ (163,994)	$ 1,672,587	$ 0