CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands	Total	PREFERRED SHARES	COMMON SHARES, $0.01 PAR VALUE	PAID IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	DISTRIBUTIONS	OPERATING PARTNERSHIP	PARTIALLY OWNED PROPERTIES
Balance, beginning of year at Dec. 31, 2019		$ 37,280	$ 3,717	$ 8,965,577	$ 1,386,495	$ (77,563)
Balance, beginning of year at Dec. 31, 2019								$ 227,837	$ 1,183
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares			1	3,912
Exercise of share options			2	11,424
Employee Share Purchase Plan (ESPP)				3,556
Share-based employee compensation expense:
Issuance of restricted units/shares			2	9,236				12
Share options				1,819
ESPP discount				626
Supplemental Executive Retirement Plan (SERP)				(395)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	$ (169,825)			169,825
Adjustment for Noncontrolling Interests ownership in Operating Partnership				438				(438)
PAID IN CAPITAL
Conversion of OP Units into Common Shares			1	3,912
Exercise of share options			2	11,424
Employee Share Purchase Plan (ESPP)				3,556
RETAINED EARNINGS
Net income attributable to controlling interests	660,780				660,780
Common Share distributions					(673,019)
Preferred Share distributions					(2,318)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(1,190)					(1,190)
Losses reclassified into earnings from other comprehensive income	(17,275)					17,275
DISTRIBUTIONS
Distributions declared per Common Share outstanding							$ 1.8075
NONCONTROLLING INTERESTS
Issuance of restricted units/shares			2	9,236				12
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(3,913)
Equity compensation associated with Noncontrolling Interests								9,525
Net income attributable to Noncontrolling Interests	24,624							24,624	14,113
Distributions to Noncontrolling Interests								(25,000)	(11,343)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership	131							(131)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				438				(438)
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	24,624							24,624	14,113
Contributions by Noncontrolling Interests									417
Distributions to Noncontrolling Interests								(25,000)	(11,343)
Balance, end of period at Sep. 30, 2020		37,280	3,722	9,166,018	1,371,938	(61,478)
Balance, end of period at Sep. 30, 2020								232,516	4,370
Balance, beginning of year at Jun. 30, 2020		37,280	3,722	9,118,332	1,505,694	(67,355)
Balance, beginning of year at Jun. 30, 2020								235,169	4,634
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares				57
Exercise of share options				104
Employee Share Purchase Plan (ESPP)				1,197
Share-based employee compensation expense:
Issuance of restricted units/shares				1,984
Share options				526
ESPP discount				210
Supplemental Executive Retirement Plan (SERP)				111
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership				41,072
Adjustment for Noncontrolling Interests ownership in Operating Partnership				2,425				(2,425)
PAID IN CAPITAL
Conversion of OP Units into Common Shares				57
Exercise of share options				104
Employee Share Purchase Plan (ESPP)				1,197
RETAINED EARNINGS
Net income attributable to controlling interests	91,286				91,286
Common Share distributions					(224,269)
Preferred Share distributions					(773)
Accumulated other comprehensive income (loss) - derivative instruments:
Losses reclassified into earnings from other comprehensive income	(5,877)					5,877
DISTRIBUTIONS
Distributions declared per Common Share outstanding							0.6025
NONCONTROLLING INTERESTS
Issuance of restricted units/shares				1,984
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(57)
Equity compensation associated with Noncontrolling Interests								2,499
Net income attributable to Noncontrolling Interests	3,376							3,376	703
Distributions to Noncontrolling Interests								(7,963)	(1,043)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership								1,917
Adjustment for Noncontrolling Interests ownership in Operating Partnership				2,425				(2,425)
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	3,376							3,376	703
Contributions by Noncontrolling Interests									76
Distributions to Noncontrolling Interests								(7,963)	(1,043)
Balance, end of period at Sep. 30, 2020		37,280	3,722	9,166,018	1,371,938	(61,478)
Balance, end of period at Sep. 30, 2020								232,516	4,370
Balance, beginning of year at Dec. 31, 2020	10,525,651	37,280	3,723	9,128,599	1,399,715	(43,666)
Balance, beginning of year at Dec. 31, 2020	237,835							233,162	4,673
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares			11	68,246
Exercise of share options			14	68,793
Employee Share Purchase Plan (ESPP)			1	3,454
Share-based employee compensation expense:
Issuance of restricted units/shares			1	6,571
Share options				2,541
ESPP discount				798
Offering costs				(267)
Supplemental Executive Retirement Plan (SERP)				(1,335)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	119,237			(119,237)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(27,085)				27,085
PAID IN CAPITAL
Conversion of OP Units into Common Shares			11	68,246
Exercise of share options			14	68,793
Employee Share Purchase Plan (ESPP)			1	3,454
RETAINED EARNINGS
Net income attributable to controlling interests	805,876				805,876
Common Share distributions					(676,158)
Preferred Share distributions					(2,318)
Accumulated other comprehensive income (loss) - derivative instruments:
Losses reclassified into earnings from other comprehensive income	(7,000)					7,000
DISTRIBUTIONS
Distributions declared per Common Share outstanding							1.8075
NONCONTROLLING INTERESTS
Issuance of restricted units/shares			1	6,571
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(68,257)
Equity compensation associated with Noncontrolling Interests								14,173
Net income attributable to Noncontrolling Interests	27,903							27,903	1,957
Distributions to Noncontrolling Interests								(23,366)	(4,492)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership	1,745							(1,745)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(27,085)				27,085
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	27,903							27,903	1,957
Distributions to Noncontrolling Interests								(23,366)	(4,492)
Balance, end of period at Sep. 30, 2021	10,662,557	37,280	3,750	9,131,078	1,527,115	(36,666)
Balance, end of period at Sep. 30, 2021	211,093							208,955	2,138
Balance, beginning of year at Jun. 30, 2021		37,280	3,744	9,110,121	1,321,875	(39,029)
Balance, beginning of year at Jun. 30, 2021								205,691	2,365
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares				1,597
Exercise of share options			6	29,178
Employee Share Purchase Plan (ESPP)				788
Share-based employee compensation expense:
Issuance of restricted units/shares				1,758
Share options				565
ESPP discount				165
Offering costs				(267)
Supplemental Executive Retirement Plan (SERP)				722
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership				(17,271)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				3,722				(3,722)
PAID IN CAPITAL
Conversion of OP Units into Common Shares				1,597
Exercise of share options			6	29,178
Employee Share Purchase Plan (ESPP)				788
RETAINED EARNINGS
Net income attributable to controlling interests	431,951				431,951
Common Share distributions					(225,938)
Preferred Share distributions					(773)
Accumulated other comprehensive income (loss) - derivative instruments:
Losses reclassified into earnings from other comprehensive income	(2,363)					2,363
DISTRIBUTIONS
Distributions declared per Common Share outstanding							$ 0.6025
NONCONTROLLING INTERESTS
Issuance of restricted units/shares				1,758
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(1,597)
Equity compensation associated with Noncontrolling Interests								3,642
Net income attributable to Noncontrolling Interests	14,847							14,847	534
Distributions to Noncontrolling Interests								(7,367)	(761)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership								(2,539)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				3,722				(3,722)
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	14,847							14,847	534
Distributions to Noncontrolling Interests								(7,367)	(761)
Balance, end of period at Sep. 30, 2021	10,662,557	$ 37,280	$ 3,750	$ 9,131,078	$ 1,527,115	$ (36,666)
Balance, end of period at Sep. 30, 2021	$ 211,093							$ 208,955	$ 2,138