Condensed Consolidated Statements of Equity - USD ($) shares in Thousands, $ 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	7,203	0	0	0	7,203	7,203	0
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Gross		89	(941)	0	0	(852)
Amortization of stock options and restricted stock, net of forfeitures	475	0	475	0	0	475	0
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(852)						0
Preferred Stock Redemption	0
Common dividends paid	(17,349)	0	0	0	(17,349)	(17,349)	0
Ending Balance at Mar. 31, 2015	1,662,935	220,172	1,720,506	(86,840)	(190,903)	1,662,935	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	22,796	$ 0	0	0	22,796	22,796	0
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Gross	(427)		(607)	0	0	(427)	0
Stock Issued During Period, Shares, Share-based Compensation, Gross		180
Amortization of stock options and restricted stock, net of forfeitures	403	$ 0	403	0	0	403	0
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	758	0	0	0	0	0	758
Preferred Stock Redemption	(13,743)	0	0	(13,743)	0	(13,743)	0
Common dividends paid	(16,918)	0	0	0	(16,918)	(16,918)	0
Ending Balance at Mar. 31, 2016	$ 1,676,284	$ 220,436	$ 1,722,020	$ (148,373)	$ (118,557)	$ 1,675,526	$ 758