Consolidated Statement of Equity - USD ($) $ in Thousands	Total	Total Shareholders’  Equity	Par Value	Additional Paid in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total Noncontrolling Interests	Operating Partnership Noncontrolling Interest	Partially Owned Properties Noncontrolling Interest
Balance at beginning of period at Dec. 31, 2020	$ 2,715,002	$ 2,641,297	$ 2,096	$ 3,303,231	$ (658,171)	$ (5,859)	$ 73,705	$ 73,302	$ 403
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from sale of common shares	52,432	52,432	28	52,404
Restricted share award grants, net	(993)	(993)	4	(333)	(664)
Purchase of OP Units	(269)						(269)	(269)
Dividends/distributions declared	(50,254)	(49,011)			(49,011)		(1,243)	(1,243)
Preferred distributions	(13)	(13)			(13)
Distributions	(73)						(73)		(73)
Change in market value of Redeemable Noncontrolling Interest in partially owned properties	873	873		(23)	896
Change in fair value of interest rate swap agreements	797	797				797
Adjustment for Noncontrolling Interests ownership in Operating Partnership	0	1,136		1,136			(1,136)	(1,136)
Net income	17,729	17,194			17,194		535	459	76
Balance at end of period at Mar. 31, 2021	2,735,231	2,663,712	2,128	3,356,415	(689,769)	(5,062)	71,519	71,113	406
Balance at beginning of period at Dec. 31, 2020	2,715,002	2,641,297	2,096	3,303,231	(658,171)	(5,859)	73,705	73,302	403
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in fair value of interest rate swap agreements	1,805
Balance at end of period at Sep. 30, 2021	2,757,911	2,690,718	2,174	3,443,748	(751,150)	(4,054)	67,193	66,736	457
Balance at beginning of period at Mar. 31, 2021	2,735,231	2,663,712	2,128	3,356,415	(689,769)	(5,062)	71,519	71,113	406
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from sale of common shares	82,827	82,827	46	82,781
Restricted share award grants, net	2,760	2,760		3,242	(482)
Purchase of OP Units	(5,063)						(5,063)	(5,063)
Dividends/distributions declared	(51,303)	(50,061)			(50,061)		(1,242)	(1,242)
Distributions	(50)						(50)		(50)
Change in market value of Redeemable Noncontrolling Interest in partially owned properties	(388)	(388)			(388)
Change in fair value of interest rate swap agreements	543	543				543
Adjustment for Noncontrolling Interests ownership in Operating Partnership	0	(2,124)		(2,124)			2,124	2,124
Net income	18,606	18,113			18,113		493	417	76
Balance at end of period at Jun. 30, 2021	2,783,163	2,715,382	2,174	3,440,314	(722,587)	(4,519)	67,781	67,349	432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from sale of common shares	(117)	(117)		(117)
Restricted share award grants, net	3,755	3,755		3,642	113
Dividends/distributions declared	(51,295)	(50,062)			(50,062)		(1,233)	(1,233)
Distributions	(51)						(51)		(51)
Change in market value of Redeemable Noncontrolling Interest in partially owned properties	22	22			22
Change in fair value of interest rate swap agreements	465	465				465
Adjustment for Noncontrolling Interests ownership in Operating Partnership	0	(91)		(91)			91	91
Net income	21,969	21,364			21,364		605	529	76
Balance at end of period at Sep. 30, 2021	2,757,911	2,690,718	2,174	3,443,748	(751,150)	(4,054)	67,193	66,736	457
Balance at beginning of period at Dec. 31, 2021	2,987,033	2,836,308	2,247	3,610,954	(776,001)	(892)	150,725	150,241	484
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from sale of common shares	5,032	5,032	3	5,029
Restricted share award grants, net	(300)	(300)	3	118	(421)
Purchase of OP Units	(184)						(184)	(184)
Dividends/distributions declared	(54,619)	(51,879)			(51,879)		(2,740)	(2,740)
Contributions	569						569		569
Distributions	(55)						(55)		(55)
Change in market value of Redeemable Noncontrolling Interest in partially owned properties	717	717			717
Change in fair value of interest rate swap agreements	1,379	1,379				1,379
Adjustment for Noncontrolling Interests ownership in Operating Partnership	0	(217)		(217)			217	217
Net income	13,866	13,092			13,092		774	692	82
Balance at end of period at Mar. 31, 2022	2,953,438	2,804,132	2,253	3,615,884	(814,492)	487	149,306	148,226	1,080
Balance at beginning of period at Dec. 31, 2021	2,987,033	2,836,308	2,247	3,610,954	(776,001)	(892)	150,725	150,241	484
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in fair value of interest rate swap agreements	6,215
Balance at end of period at Sep. 30, 2022	2,965,382	2,817,845	2,268	3,648,983	(838,729)	5,323	147,537	146,426	1,111
Balance at beginning of period at Mar. 31, 2022	2,953,438	2,804,132	2,253	3,615,884	(814,492)	487	149,306	148,226	1,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from sale of common shares	18,484	18,484	9	18,475
Restricted share award grants, net	2,678	2,678	1	3,588	(911)
Dividends/distributions declared	(54,828)	(52,116)			(52,116)		(2,712)	(2,712)
Distributions	(61)						(61)		(61)
Change in market value of Redeemable Noncontrolling Interest in partially owned properties	527	527			527
Change in fair value of interest rate swap agreements	3,083	3,083				3,083
Adjustment for Noncontrolling Interests ownership in Operating Partnership	0	(488)		(488)			488	488
Net income	17,856	16,891			16,891		965	886	79
Balance at end of period at Jun. 30, 2022	2,941,177	2,793,191	2,263	3,637,459	(850,101)	3,570	147,986	146,888	1,098
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from sale of common shares	7,930	7,930	5	7,925
Restricted share award grants, net	3,790	3,790		4,326	(536)
Purchase of OP Units	(2,139)						(2,139)	(2,139)
Dividends/distributions declared	(54,865)	(52,563)			(52,563)		(2,302)	(2,302)
Distributions	(61)						(61)		(61)
Change in market value of Redeemable Noncontrolling Interest in partially owned properties	1,513	1,513			1,513
Change in fair value of interest rate swap agreements	1,753	1,753				1,753
Adjustment for Noncontrolling Interests ownership in Operating Partnership	0	(727)		(727)			727	727
Net income	66,284	62,958			62,958		3,326	3,252	74
Balance at end of period at Sep. 30, 2022	$ 2,965,382	$ 2,817,845	$ 2,268	$ 3,648,983	$ (838,729)	$ 5,323	$ 147,537	$ 146,426	$ 1,111