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	68,774	0	0	0	68,774	68,774	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	68,774
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	1,104	0	1,104	0	0	1,104	0
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(71)						0
Preferred Stock Redemption	18,691	0	0	18,691	0	18,691	0
Common dividends paid	(52,011)	0	0	0	(52,011)	(52,011)	0
Ending Balance at Sep. 30, 2015	1,672,587	220,256	1,721,856	(105,531)	(163,994)	1,672,587	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	42,218	0	0	0		42,218	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	42,218
Common stock issued pursuant to:
Stock Granted, Value, Share-based Compensation, Gross	333	257	76	0	0	333	0
Amortization of stock options and restricted stock, net of forfeitures	1,238	(14)	1,252	0	0	1,238	0
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	2,525	0	0	0	0	0	2,525
Preferred Stock Redemption	(13,743)	0	0	(13,743)	0	(13,743)	0
Common dividends paid	(50,549)	0	0	0	(50,549)	(50,549)	0
Ending Balance at Sep. 30, 2016	$ 1,665,437	$ 220,499	$ 1,723,552	$ (148,373)	$ (132,766)	$ 1,662,912	$ 2,525