CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Parent	Preferred Stock	Common Stock	Capital in Excess of Par Value	Cumulative Net Income	Accumulated Other Comprehensive Income (Loss)	Cumulative Distributions	Non-controlling Interests	Total
Balance - beginning of period at Dec. 31, 2014	$ 660,121	$ 38,500	$ 355	$ 717,396	$ 855,247	$ 82	$ (951,459)		$ 660,121
Balance (in shares) at Dec. 31, 2014		2,000	35,480
Equity activity
Reclassification adjustment	(35)					(35)			(35)
Issuance of restricted stock			$ 1	(1)
Issuance of restricted stock (in shares)			92
Net income	73,081				73,081				73,081
Vesting of restricted stock	3,992			3,992					3,992
Vested stock options	14			14					14
Stock option exercises	79			79					79
Options exercised (in shares)			3
Conversion of Series C Preferred Stock		$ (38,500)	$ 20	38,480
Conversion of Series C Preferred Stock (in shares)		(2,000)	2,000
Preferred stock dividends	(2,454)						(2,454)		(2,454)
Common stock cash distributions (2017 - $2.28, 2016 - $2.19 and 2015 - $2.07 per share)	(74,311)						(74,311)		(74,311)
Other	(1,285)		$ (1)	(1,284)					(1,285)
Other (in shares)			(27)
Balance - end of period at Dec. 31, 2015	659,202		$ 375	758,676	928,328	47	(1,028,224)		659,202
Balance (in shares) at Dec. 31, 2015			37,548
Equity activity
Reclassification adjustment	(47)					$ (47)			(47)
Issuance of common stock	78,136		$ 16	78,120					78,136
Issuance of common stock (in shares)			1,643
Issuance of restricted stock	(41)		$ 1	(42)					(41)
Issuance of restricted stock (in shares)			73
Net income	85,115				85,115				85,115
Vesting of restricted stock	4,265			4,265					4,265
Vested stock options	15			15					15
Stock option exercises	159			159					159
Options exercised (in shares)			7
Common stock cash distributions (2017 - $2.28, 2016 - $2.19 and 2015 - $2.07 per share)	(84,568)						(84,568)		(84,568)
Other	(2,188)			(2,188)					(2,188)
Other (in shares)			(50)
Balance - end of period at Dec. 31, 2016	740,048		$ 392	839,005	1,013,443		(1,112,792)		740,048
Balance (in shares) at Dec. 31, 2016			39,221
Equity activity
Issuance of common stock	14,529		$ 3	14,526					14,529
Issuance of common stock (in shares)			313
Issuance of restricted stock	(20)		$ 1	(21)					(20)
Issuance of restricted stock (in shares)			85
Net income	87,340				87,340				87,340
Vesting of restricted stock	5,247			5,247					5,247
Vested stock options	2			2					2
Stock option exercises	202			202					202
Options exercised (in shares)			8
Non-controlling interests contribution								$ 3,488	3,488
Common stock cash distributions (2017 - $2.28, 2016 - $2.19 and 2015 - $2.07 per share)	(90,219)						(90,219)		(90,219)
Other	(1,969)			(1,969)					(1,969)
Other (in shares)			(57)
Balance - end of period at Dec. 31, 2017	$ 755,160		$ 396	$ 856,992	$ 1,100,783		$ (1,203,011)	$ 3,488	$ 758,648
Balance (in shares) at Dec. 31, 2017			39,570