CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - 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, 2017		$ 37,280	$ 3,680	$ 8,886,586	$ 1,403,530	$ (88,612)
Balance, beginning of year at Dec. 31, 2017								$ 226,691	$ 4,708
Conversion of OP Units into Common Shares			1	4,097
Exercise of share options			11	30,644
Employee Share Purchase Plan (ESPP)	$ 3,879		1	3,878
Issuance of restricted units/shares			1	8,257				1
Share options				9,734
ESPP discount				767
Offering costs				(27)
Supplemental Executive Retirement Plan (SERP)				(454)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	13,922			(13,922)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				5,893				(5,893)
Net income attributable to controlling interests	657,535				657,535
Common Share distributions					(796,212)
Preferred Share distributions					(3,090)
Unrealized holding gains (losses) arising during the year	5,174					5,174
Losses reclassified into earnings from other comprehensive income	(18,452)					18,452
Distributions declared per Common Share outstanding							$ 2.16
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(4,098)
Equity compensation associated with Noncontrolling Interests								14,009
Net income attributable to Noncontrolling Interests	24,939							24,939	2,718
Acquisitions of Noncontrolling Interests – Partially Owned Properties									(13)
Contributions by Noncontrolling Interests									125
Distributions to Noncontrolling Interests								(28,682)	(9,831)
Change in carrying value of Redeemable Noncontrolling Interests –Operating Partnership	(1,771)							1,771
Balance, end of year at Dec. 31, 2018		37,280	3,694	8,935,453	1,261,763	(64,986)
Balance, end of year at Dec. 31, 2018								228,738	(2,293)
Conversion of OP Units into Common Shares			3	10,407
Exercise of share options			17	77,768
Employee Share Purchase Plan (ESPP)	3,116		1	3,115
Issuance of restricted units/shares			2	12,436				2
Share options				2,675
ESPP discount				642
Offering costs				(991)
Supplemental Executive Retirement Plan (SERP)				(1,675)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	82,283			(82,283)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				8,030				(8,030)
Net income attributable to controlling interests	970,377				970,377
Common Share distributions					(842,555)
Preferred Share distributions					(3,090)
Unrealized holding gains (losses) arising during the year	(33,765)					(33,765)
Losses reclassified into earnings from other comprehensive income	(21,188)					21,188
Distributions declared per Common Share outstanding							2.27
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(10,410)
Equity compensation associated with Noncontrolling Interests								13,410
Net income attributable to Noncontrolling Interests	36,034							36,034	3,297
Contributions by Noncontrolling Interests									7,337
Distributions to Noncontrolling Interests								(29,896)	(7,158)
Change in carrying value of Redeemable Noncontrolling Interests –Operating Partnership	2,011							(2,011)
Balance, end of year at Dec. 31, 2019	10,315,506	37,280	3,717	8,965,577	1,386,495	(77,563)
Balance, end of year at Dec. 31, 2019	229,020							227,837	1,183
Conversion of OP Units into Common Shares			1	4,695
Exercise of share options			2	12,273
Employee Share Purchase Plan (ESPP)	4,508		1	4,507
Issuance of restricted units/shares			2	11,223				13
Share options				2,349
ESPP discount				944
Supplemental Executive Retirement Plan (SERP)				(395)
Change in market value of Redeemable Noncontrolling Interests –Operating Partnership	(125,224)			125,224
Adjustment for Noncontrolling Interests ownership in Operating Partnership				2,202				(2,202)
Net income attributable to controlling interests	913,636				913,636
Common Share distributions					(897,326)
Preferred Share distributions					(3,090)
Unrealized holding gains (losses) arising during the year	(1,190)					(1,190)
Losses reclassified into earnings from other comprehensive income	(35,087)					35,087
Distributions declared per Common Share outstanding							$ 2.41
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(4,696)
Equity compensation associated with Noncontrolling Interests								11,926
Net income attributable to Noncontrolling Interests	34,010							34,010	14,855
Contributions by Noncontrolling Interests									417
Distributions to Noncontrolling Interests								(32,951)	(11,782)
Change in carrying value of Redeemable Noncontrolling Interests –Operating Partnership	775							(775)
Balance, end of year at Dec. 31, 2020	10,525,651	$ 37,280	$ 3,723	$ 9,128,599	$ 1,399,715	$ (43,666)
Balance, end of year at Dec. 31, 2020	$ 237,835							$ 233,162	$ 4,673