CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	PREFERRED SHARES	COMMON SHARES, $0.01 PAR VALUE	PAID IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	OPERATING PARTNERSHIP	PARTIALLY OWNED PROPERTIES
Balance, beginning of year at Dec. 31, 2017	$ 10,242,464	$ 37,280	$ 3,680	$ 8,886,586	$ 1,403,530	$ (88,612)
Balance, beginning of year at Dec. 31, 2017	231,399						$ 226,691	$ 4,708
COMMON SHARES, $0.01 PAR VALUE
Conversion of OP Units into Common Shares				134			(134)
Exercise of share options			1	1,599
Employee Share Purchase Plan (ESPP)				1,681
Restricted shares			1	2,622
Share options				7,338
ESPP discount				297
PAID IN CAPITAL
Conversion of OP Units into Common Shares				134			(134)
Exercise of share options			1	1,599
Employee Share Purchase Plan (ESPP)				1,681
Share-based employee compensation expense:
Offering costs				(26)
Supplemental Executive Retirement Plan (SERP)				83
Change in market value of Redeemable Noncontrolling Interests – Operating Partnership	(12,831)			12,831
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(2,839)			2,839
RETAINED EARNINGS
Net income attributable to controlling interests	211,809				211,809
Common Share distributions					(198,928)
Preferred Share distributions					(773)
Accumulated other comprehensive income (loss) – derivative instruments:
Unrealized holding gains (losses) arising during the period	6,087					6,087
Losses reclassified into earnings from other comprehensive income	(4,791)					4,791
NONCONTROLLING INTERESTS
Issuance of restricted units to Noncontrolling Interests							1
Conversion of OP Units into Common Shares				134			(134)
Equity compensation associated with Noncontrolling Interests							4,803
Net income	220,548
Distributions to Noncontrolling Interests							(7,188)	(4,220)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership	443						(443)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(2,839)			2,839
Net income attributable to Noncontrolling Interests	8,059						8,059	680
PARTIALLY OWNED PROPERTIES
Net income	220,548
Distributions to Noncontrolling Interests							(7,188)	(4,220)
Net income attributable to Noncontrolling Interests	8,059						8,059	680
Contributions by Noncontrolling Interests								125
Balance, end of period at Mar. 31, 2018	10,289,172	$ 37,280	$ 3,682	$ 8,910,306	$ 1,415,638	$ (77,734)
Balance, end of period at Mar. 31, 2018	$ 235,921						$ 234,628	$ 1,293