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	3,855
Exercise of share options			2	11,320
Employee Share Purchase Plan (ESPP)				2,359
Share-based employee compensation expense:
Issuance of restricted units/shares			2	7,252				12
Share options				1,293
ESPP discount				416
Supplemental Executive Retirement Plan (SERP)				(506)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	$ (128,753)			128,753
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(1,987)				1,987
PAID IN CAPITAL
Conversion of OP Units into Common Shares			1	3,855
Exercise of share options			2	11,320
Employee Share Purchase Plan (ESPP)				2,359
RETAINED EARNINGS
Net income attributable to controlling interests	569,494				569,494
Common Share distributions					(448,750)
Preferred Share distributions					(1,545)
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	(11,398)					11,398
DISTRIBUTIONS
Distributions declared per Common Share outstanding							$ 1.205
NONCONTROLLING INTERESTS
Issuance of restricted units/shares			2	7,252				12
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(3,856)
Equity compensation associated with Noncontrolling Interests								7,026
Net income attributable to Noncontrolling Interests	21,248							21,248	13,410
Distributions to Noncontrolling Interests								(17,037)	(10,300)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership	2,048							(2,048)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(1,987)				1,987
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	21,248							21,248	13,410
Contributions by Noncontrolling Interests									341
Distributions to Noncontrolling Interests								(17,037)	(10,300)
Balance, end of period at Jun. 30, 2020		37,280	3,722	9,118,332	1,505,694	(67,355)
Balance, end of period at Jun. 30, 2020								235,169	4,634
Balance, beginning of year at Mar. 31, 2020		37,280	3,721	9,092,441	1,469,821	(72,896)
Balance, beginning of year at Mar. 31, 2020								235,580	4,739
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares			1	2,011
Exercise of share options				171
Employee Share Purchase Plan (ESPP)				1,490
Share-based employee compensation expense:
Issuance of restricted units/shares				3,231
Share options				623
ESPP discount				263
Supplemental Executive Retirement Plan (SERP)				(655)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership				17,304
Adjustment for Noncontrolling Interests ownership in Operating Partnership				1,453				(1,453)
PAID IN CAPITAL
Conversion of OP Units into Common Shares			1	2,011
Exercise of share options				171
Employee Share Purchase Plan (ESPP)				1,490
RETAINED EARNINGS
Net income attributable to controlling interests	260,888				260,888
Common Share distributions					(224,243)
Preferred Share distributions					(772)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(223)					(223)
Losses reclassified into earnings from other comprehensive income	(5,764)					5,764
DISTRIBUTIONS
Distributions declared per Common Share outstanding							0.6025
NONCONTROLLING INTERESTS
Issuance of restricted units/shares				3,231
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(2,012)
Equity compensation associated with Noncontrolling Interests								1,959
Net income attributable to Noncontrolling Interests	9,713							9,713	880
Distributions to Noncontrolling Interests								(7,961)	(985)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership								(657)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				1,453				(1,453)
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	9,713							9,713	880
Distributions to Noncontrolling Interests								(7,961)	(985)
Balance, end of period at Jun. 30, 2020		37,280	3,722	9,118,332	1,505,694	(67,355)
Balance, end of period at Jun. 30, 2020								235,169	4,634
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	66,649
Exercise of share options			8	39,615
Employee Share Purchase Plan (ESPP)			1	2,666
Share-based employee compensation expense:
Issuance of restricted units/shares			1	4,813
Share options				1,976
ESPP discount				633
Supplemental Executive Retirement Plan (SERP)				(2,057)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	101,966			(101,966)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(30,807)				30,807
PAID IN CAPITAL
Conversion of OP Units into Common Shares			11	66,649
Exercise of share options			8	39,615
Employee Share Purchase Plan (ESPP)			1	2,666
RETAINED EARNINGS
Net income attributable to controlling interests	373,925				373,925
Common Share distributions					(450,220)
Preferred Share distributions					(1,545)
Accumulated other comprehensive income (loss) - derivative instruments:
Losses reclassified into earnings from other comprehensive income	(4,637)					4,637
DISTRIBUTIONS
Distributions declared per Common Share outstanding							1.205
NONCONTROLLING INTERESTS
Issuance of restricted units/shares			1	4,813
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(66,660)
Equity compensation associated with Noncontrolling Interests								10,531
Net income attributable to Noncontrolling Interests	13,056							13,056	1,423
Distributions to Noncontrolling Interests								(15,999)	(3,731)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership	(794)							794
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(30,807)				30,807
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	13,056							13,056	1,423
Distributions to Noncontrolling Interests								(15,999)	(3,731)
Balance, end of period at Jun. 30, 2021	10,433,991	37,280	3,744	9,110,121	1,321,875	(39,029)
Balance, end of period at Jun. 30, 2021	208,056							205,691	2,365
Balance, beginning of year at Mar. 31, 2021		37,280	3,729	9,083,346	1,231,808	(41,363)
Balance, beginning of year at Mar. 31, 2021								234,969	2,472
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares			11	66,649
Exercise of share options			3	16,738
Employee Share Purchase Plan (ESPP)			1	935
Share-based employee compensation expense:
Issuance of restricted units/shares				2,540
Share options				988
ESPP discount				189
Supplemental Executive Retirement Plan (SERP)				(828)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership				(29,010)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(31,426)				31,426
PAID IN CAPITAL
Conversion of OP Units into Common Shares			11	66,649
Exercise of share options			3	16,738
Employee Share Purchase Plan (ESPP)			1	935
RETAINED EARNINGS
Net income attributable to controlling interests	316,386				316,386
Common Share distributions					(225,547)
Preferred Share distributions					(772)
Accumulated other comprehensive income (loss) - derivative instruments:
Losses reclassified into earnings from other comprehensive income	(2,334)					2,334
DISTRIBUTIONS
Distributions declared per Common Share outstanding							$ 0.6025
NONCONTROLLING INTERESTS
Issuance of restricted units/shares				2,540
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(66,660)
Equity compensation associated with Noncontrolling Interests								4,043
Net income attributable to Noncontrolling Interests	10,913							10,913	741
Distributions to Noncontrolling Interests								(7,410)	(848)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership								(1,590)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(31,426)				31,426
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	10,913							10,913	741
Distributions to Noncontrolling Interests								(7,410)	(848)
Balance, end of period at Jun. 30, 2021	10,433,991	$ 37,280	$ 3,744	$ 9,110,121	$ 1,321,875	$ (39,029)
Balance, end of period at Jun. 30, 2021	$ 208,056							$ 205,691	$ 2,365