Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment	Cumulative Effect, Period Of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period Of Adoption, Adjusted Balance	Paid-in Capital	Paid-in Capital Cumulative Effect, Period Of Adoption, Adjusted Balance	Redeemable Perpetual Preferred Stock	Redeemable Perpetual Preferred Stock Cumulative Effect, Period Of Adoption, Adjusted Balance	Distributions in Excess of Accumulated Earnings	Distributions in Excess of Accumulated Earnings Cumulative Effect, Period Of Adoption, Adjustment	Distributions in Excess of Accumulated Earnings Cumulative Effect, Period Of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period Of Adoption, Adjusted Balance	Non-controlling interests – Common OP Units	Non-controlling interests – Common OP Units Cumulative Effect, Period Of Adoption, Adjusted Balance
Beginning balance at Dec. 31, 2019	$ 1,321,888	$ (3,875)	$ 1,318,013	$ 1,812	$ 1,812	$ 1,402,696	$ 1,402,696	$ 0	$ 0	$ (154,318)	$ (3,875)	$ (158,193)	$ (380)	$ (380)	$ 72,078	$ 72,078
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP units for common stock (in shares)				0
Exchange of Common OP Units for Common Stock	0					63									(63)
Issuance of Common Stock through employee stock purchase plan	619					619
Compensation expenses related to restricted stock and stock options	2,964					2,964
Repurchase of Common Stock or Common OP Units	(3,962)					(3,962)
Adjustment for Common OP Unitholders in the Operating Partnership	0					277									(277)
Adjustment for fair market value of swap	(1,333)												(1,333)
Consolidated net income	70,724							0		66,875					3,849
Distributions	(65,975)							0		(62,385)					(3,590)
Other	(143)					(143)
Ending balance at Mar. 31, 2020	1,320,907			$ 1,812		1,402,514		0		(153,703)			(1,713)		71,997
Beginning balance at Dec. 31, 2019	$ 1,321,888	$ (3,875)	$ 1,318,013	1,812	$ 1,812	1,402,696	$ 1,402,696	0	$ 0	(154,318)	$ (3,875)	$ (158,193)	(380)	$ (380)	72,078	$ 72,078
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP units for common stock (in shares)	9,228
Adjustment for fair market value of swap	$ (781)
Ending balance at Jun. 30, 2020	1,307,383			1,812		1,405,764		0		(169,903)			(1,161)		70,871
Beginning balance at Mar. 31, 2020	1,320,907			1,812		1,402,514		0		(153,703)			(1,713)		71,997
Increase (Decrease) in Stockholders' Equity
Issuance of Common Stock through employee stock purchase plan	531					531
Compensation expenses related to restricted stock and stock options	2,669					2,669
Adjustment for Common OP Unitholders in the Operating Partnership	0					193									(193)
Adjustment for fair market value of swap	552												552
Consolidated net income	48,853							8		46,187					2,658
Distributions	(65,986)							(8)		(62,387)					(3,591)
Other	(143)					(143)
Ending balance at Jun. 30, 2020	1,307,383			1,812		1,405,764		0		(169,903)			(1,161)		70,871
Beginning balance at Dec. 31, 2020	1,304,755			$ 1,813		1,411,397		0		(179,523)			0		71,068
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP units for common stock (in shares)				0
Exchange of Common OP Units for Common Stock	0					58									(58)
Issuance of Common Stock through employee stock purchase plan	732					732
Compensation expenses related to restricted stock and stock options	2,556					2,556
Repurchase of Common Stock or Common OP Units	(2,814)					(2,814)
Adjustment for fair market value of swap	129												129
Consolidated net income	68,987							0		65,240					3,747
Distributions	(69,883)							0		(66,087)					(3,796)
Other	(116)					(116)
Ending balance at Mar. 31, 2021	1,304,346			$ 1,813		1,411,813		0		(180,370)			129		70,961
Beginning balance at Dec. 31, 2020	$ 1,304,755			1,813		1,411,397		0		(179,523)			0		71,068
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP units for common stock (in shares)	1,386,716
Adjustment for fair market value of swap	$ 239
Ending balance at Jun. 30, 2021	1,301,991			1,827		1,424,350		0		(185,930)			239		61,505
Beginning balance at Mar. 31, 2021	1,304,346			$ 1,813		1,411,813		0		(180,370)			129		70,961
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP units for common stock (in shares)				14,000
Exchange of Common OP Units for Common Stock	0					9,310									(9,324)
Issuance of Common Stock through employee stock purchase plan	605					605
Compensation expenses related to restricted stock and stock options	2,821					2,821
Adjustment for Common OP Unitholders in the Operating Partnership	0					(143)									143
Adjustment for fair market value of swap	110												110
Consolidated net income	64,080							8		61,051					3,021
Distributions	(69,915)							(8)		(66,611)					(3,296)
Other	(56)					(56)
Ending balance at Jun. 30, 2021	$ 1,301,991			$ 1,827		$ 1,424,350		$ 0		$ (185,930)			$ 239		$ 61,505