Condensed Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Distributions in Excess of Net Income	Stockholders' Investment	Nonredeemable Noncontrolling Interests
Beginning Balance at Dec. 31, 2014	$ 1,673,458	$ 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	15,155	0	0	0	15,155	15,155	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	15,155
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Gross		173	(244)	0	0	(71)
Amortization of stock options and restricted stock, net of forfeitures	808	0	808	0	0	808	0
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(71)						0
Common dividends paid	(34,677)	0	0	0	(34,677)	(34,677)	0
Ending Balance at Jun. 30, 2015	1,654,697	220,256	1,721,560	(86,840)	(200,279)	1,654,697	0
Common stock issued pursuant to:
Stockholders' Equity, Other	(24)	0	(24)	0	0	(24)	0
Beginning Balance at Dec. 31, 2015	1,683,415	220,256	1,722,224	(134,630)	(124,435)	1,683,415	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	30,561	0	0			30,561	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	30,561				30,561
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Gross	339		81	0	0	339	0
Amortization of stock options and restricted stock, net of forfeitures	813	(13)	826	0	0	813	0
Preferred Stock Redemption	(13,743)	0	0	(13,743)	0	(13,743)	0
Common dividends paid	(33,728)	0	0	0	(33,728)	(33,728)	0
Ending Balance at Jun. 30, 2016	$ 1,669,130	$ 220,501	$ 1,723,131	$ (148,373)	$ (127,602)	$ 1,667,657	$ 1,473