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, 2018		$ 37,280	$ 3,694	$ 8,935,453	$ 1,261,763	$ (64,986)
Balance, beginning of year at Dec. 31, 2018								$ 228,738	$ (2,293)
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares			2	4,785
Exercise of share options			7	29,853
Employee Share Purchase Plan (ESPP)				1,126
Share-based employee compensation expense:
Restricted shares			2	4,576
Share options				793
ESPP discount				267
Supplemental Executive Retirement Plan (SERP)				(602)
Change in market value of Redeemable Noncontrolling Interests – Operating Partnership	$ 55,021			(55,021)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				4,652				(4,652)
PAID IN CAPITAL
Conversion of OP Units into Common Shares			2	4,785
Exercise of share options			7	29,853
Employee Share Purchase Plan (ESPP)				1,126
RETAINED EARNINGS
Net income attributable to controlling interests	104,539				104,539
Common Share distributions					(210,497)
Preferred Share distributions					(773)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(14,420)					(14,420)
Losses reclassified into earnings from other comprehensive income	(4,393)					4,393
DISTRIBUTIONS
Distributions declared per Common Share outstanding							$ 0.5675
NONCONTROLLING INTERESTS
Conversion of OP Units into Common Shares			2	4,785
Equity compensation associated with Noncontrolling Interests								7,903
Net income	109,257
Distributions to Noncontrolling Interests								(7,605)	(3,968)
Change in carrying value of Redeemable Noncontrolling Interests – Operating Partnership	(1,565)							1,565
Adjustment for Noncontrolling Interests ownership in Operating Partnership				4,652				(4,652)
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(4,787)
Net income attributable to Noncontrolling Interests	3,919							3,919	799
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	3,919							3,919	799
Distributions to Noncontrolling Interests								(7,605)	(3,968)
Balance, end of period at Mar. 31, 2019		37,280	3,705	8,925,882	1,155,032	(75,013)
Balance, end of period at Mar. 31, 2019								225,081	(5,462)
Balance, beginning of year at Dec. 31, 2019	10,315,506	37,280	3,717	8,965,577	1,386,495	(77,563)
Balance, beginning of year at Dec. 31, 2019	229,020							227,837	1,183
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares				1,844
Exercise of share options			2	11,149
Employee Share Purchase Plan (ESPP)				869
Share-based employee compensation expense:
Restricted shares			2	4,021
Share options				670
ESPP discount				153
Supplemental Executive Retirement Plan (SERP)				149
Change in market value of Redeemable Noncontrolling Interests – Operating Partnership	(111,449)			111,449
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(3,440)				3,440
PAID IN CAPITAL
Conversion of OP Units into Common Shares				1,844
Exercise of share options			2	11,149
Employee Share Purchase Plan (ESPP)				869
RETAINED EARNINGS
Net income attributable to controlling interests	308,606				308,606
Common Share distributions					(224,507)
Preferred Share distributions					(773)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(967)					(967)
Losses reclassified into earnings from other comprehensive income	(5,634)					5,634
DISTRIBUTIONS
Distributions declared per Common Share outstanding							$ 0.6025
NONCONTROLLING INTERESTS
Issuance of restricted units to Noncontrolling Interests								12
Conversion of OP Units into Common Shares				1,844
Equity compensation associated with Noncontrolling Interests								5,067
Net income	332,671
Distributions to Noncontrolling Interests								(9,076)	(9,315)
Change in carrying value of Redeemable Noncontrolling Interests – Operating Partnership	1,391							(1,391)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(3,440)				3,440
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner								(1,844)
Net income attributable to Noncontrolling Interests	11,535							11,535	12,530
PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	11,535							11,535	12,530
Contributions by Noncontrolling Interests									341
Distributions to Noncontrolling Interests								(9,076)	(9,315)
Balance, end of period at Mar. 31, 2020	10,530,367	$ 37,280	$ 3,721	$ 9,092,441	$ 1,469,821	$ (72,896)
Balance, end of period at Mar. 31, 2020	$ 240,319							$ 235,580	$ 4,739