CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Parent Cumulative Effect of Adoption	Parent As Adjusted Balance	Parent	Common Stock As Adjusted Balance	Common Stock	Capital in Excess of Par Value As Adjusted Balance	Capital in Excess of Par Value	Cumulative Net Income Cumulative Effect of Adoption	Cumulative Net Income As Adjusted Balance	Cumulative Net Income	Cumulative Distributions As Adjusted Balance	Cumulative Distributions	Non-controlling Interests As Adjusted Balance	Non-controlling Interests	Cumulative Effect of Adoption	As Adjusted Balance	Total
Balance at beginning of period at Dec. 31, 2018	$ (42,808)	$ 782,682	$ 825,490	$ 397	$ 397	$ 862,712	$ 862,712	$ (42,808)	$ 1,212,956	$ 1,255,764	$ (1,293,383)	$ (1,293,383)	$ 7,481	$ 7,481	$ (42,808)	$ 790,163	$ 832,971
Balance (in shares) at Dec. 31, 2018				39,657	39,657
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 (in shares)					48
Issuance of restricted stock			(1)				(1)										(1)
Issuance of restricted stock (in shares)					78
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)
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
Balance at beginning of period at Dec. 31, 2018	$ (42,808)	$ 782,682	825,490	$ 397	$ 397	$ 862,712	862,712	$ (42,808)	$ 1,212,956	1,255,764	$ (1,293,383)	(1,293,383)	$ 7,481	7,481	$ (42,808)	$ 790,163	832,971
Balance (in shares) at Dec. 31, 2018				39,657	39,657
Equity activity
Net income																	68,241
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
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
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
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
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
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
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
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 (in shares)					82
Issuance of restricted stock					$ 1		(1)
Issuance of restricted stock (in shares)					76
Repurchase of common stock			(18,012)		$ (6)		(18,006)										(18,012)
Repurchase of common stock (in shares)					(616)
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)
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
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
Equity activity
Net income																	78,012
Balance at end of period at Sep. 30, 2020			770,417		$ 392		851,000			1,371,202		(1,452,177)		8,404			778,821
Balance (in shares) at Sep. 30, 2020					39,242
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
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
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
Equity activity
Common stock cash distributions			(22,368)									(22,368)					(22,368)
Stock-based compensation expense			1,693				1,693										1,693
Net income			12,217							12,217				121			12,338
Non-controlling interest distributions														(128)			(128)
Other			(19)				(19)										(19)
Other (in shares)					(1)
Balance at end of period at Sep. 30, 2020			$ 770,417		$ 392		$ 851,000			$ 1,371,202		$ (1,452,177)		$ 8,404			$ 778,821
Balance (in shares) at Sep. 30, 2020					39,242