CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Parent	Common Stock	Capital in Excess of Par Value	Cumulative Net Income	Cumulative Distributions	Non-controlling Interests	Total
Balance at beginning of period at Dec. 31, 2018	$ 825,490	$ 397	$ 862,712	$ 1,255,764	$ (1,293,383)	$ 7,481	$ 832,971
Balance (in shares) at Dec. 31, 2018		39,657,000
Equity activity
Common stock cash distributions	(22,631)				(22,631)		(22,631)
Vesting of performance-based stock units	(300)				(300)		(300)
Vesting of performance-based stock units		48,000
Issuance of restricted stock	(1)		(1)				(1)
Issuance of restricted stock (in shares)		78,000
Stock-based compensation expense	1,689		1,689				1,689
Net income	20,346			20,346		81	20,427
Non-controlling interests contributions						919	919
Non-controlling interest distributions						(89)	(89)
Other	(2,024)		(2,024)				(2,024)
Other (in shares)		(44,000)
Balance at end of period at Mar. 31, 2019	779,761	$ 397	862,376	1,233,302	(1,316,314)	8,392	788,153
Balance (in shares) at Mar. 31, 2019		39,739,000
Balance at beginning of period at Dec. 31, 2018	825,490	$ 397	862,712	1,255,764	(1,293,383)	7,481	$ 832,971
Balance (in shares) at Dec. 31, 2018		39,657,000
Equity activity
Stock option exercises (in shares)							0
Net income							$ 40,961
Balance at end of period at Jun. 30, 2019	779,171	$ 397	863,993	1,253,748	(1,338,967)	8,439	787,610
Balance (in shares) at Jun. 30, 2019		39,747,000
Equity activity
Cumulative effect of the adoption of the ASC 842	(42,808)			(42,808)			(42,808)
As Adjusted Balance at January 1, 2019	782,682	$ 397	862,712	1,212,956	(1,293,383)	7,481	790,163
Balance at beginning of period at Mar. 31, 2019	779,761	$ 397	862,376	1,233,302	(1,316,314)	8,392	788,153
Balance (in shares) at Mar. 31, 2019		39,739,000
Equity activity
Common stock cash distributions	(22,653)				(22,653)		(22,653)
Issuance of restricted stock	(6)		(6)				(6)
Issuance of restricted stock (in shares)		8,000
Stock-based compensation expense	1,623		1,623				1,623
Net income	20,446			20,446		88	20,534
Non-controlling interests contributions						46	46
Non-controlling interest distributions						(87)	(87)
Balance at end of period at Jun. 30, 2019	779,171	$ 397	863,993	1,253,748	(1,338,967)	8,439	787,610
Balance (in shares) at Jun. 30, 2019		39,747,000
Equity activity
Common stock cash distributions	(22,658)				(22,658)		(22,658)
Stock option exercises	123	$ 1	122				123
Stock option exercises (in shares)		5,000
Stock-based compensation expense	1,626		1,626				1,626
Net income	27,192			27,192		88	27,280
Non-controlling interest distributions						(67)	(67)
Other	(20)		(20)				(20)
Balance at end of period at Sep. 30, 2019	785,434	$ 398	865,721	1,280,940	(1,361,625)	8,460	793,894
Balance (in shares) at Sep. 30, 2019		39,752,000
Equity activity
Common stock cash distributions	(22,658)				(22,658)		(22,658)
Stock-based compensation expense	1,625		1,625				1,625
Net income	12,542			12,542		89	12,631
Non-controlling interest distributions						(66)	(66)
Balance at end of period at Dec. 31, 2019	776,943	$ 398	867,346	1,293,482	(1,384,283)	8,483	785,426
Balance (in shares) at Dec. 31, 2019		39,752,000
Equity activity
Common stock cash distributions	(22,581)				(22,581)		(22,581)
Vesting of performance-based stock units	(586)				(586)		(586)
Vesting of performance-based stock units		82,000
Issuance of restricted stock		$ 1	(1)
Issuance of restricted stock (in shares)		76,000
Repurchase of common stock	(18,012)	$ (6)	(18,006)				(18,012)
Repurchase of common stock (in shares)		(616,000)
Stock-based compensation expense	1,777		1,777				1,777
Net income	63,633			63,633		89	63,722
Non-controlling interest distributions						(146)	(146)
Other	(3,545)	$ (1)	(3,544)				(3,545)
Other (in shares)		(76,000)
Balance at end of period at Mar. 31, 2020	797,629	$ 392	847,572	1,357,115	(1,407,450)	8,426	806,055
Balance (in shares) at Mar. 31, 2020		39,218,000
Balance at beginning of period at Dec. 31, 2019	776,943	$ 398	867,346	1,293,482	(1,384,283)	8,483	$ 785,426
Balance (in shares) at Dec. 31, 2019		39,752,000
Equity activity
Stock option exercises (in shares)							0
Net income							$ 65,674
Balance at end of period at Jun. 30, 2020	778,894	$ 392	849,326	1,358,985	(1,429,809)	8,411	787,305
Balance (in shares) at Jun. 30, 2020		39,243,000
Balance at beginning of period at Mar. 31, 2020	797,629	$ 392	847,572	1,357,115	(1,407,450)	8,426	806,055
Balance (in shares) at Mar. 31, 2020		39,218,000
Equity activity
Common stock cash distributions	(22,359)				(22,359)		(22,359)
Issuance of restricted stock	(7)		(7)				(7)
Issuance of restricted stock (in shares)		25,000
Stock-based compensation expense	1,761		1,761				1,761
Net income	1,870			1,870		82	1,952
Non-controlling interest distributions						(97)	(97)
Balance at end of period at Jun. 30, 2020	$ 778,894	$ 392	$ 849,326	$ 1,358,985	$ (1,429,809)	$ 8,411	$ 787,305
Balance (in shares) at Jun. 30, 2020		39,243,000