CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Additional Paid-in Capital [Member]	PREFERRED SHARES	COMMON SHARES, $0.01 PAR VALUE	RETAINED EARNINGS	Accumulated Other Comprehensive (Loss)	OPERATING PARTNERSHIP	Partially Owned Properties [Member]
Beginning Balance, Noncontrolling Interest at Dec. 31, 2014	$ 339,320						$ 214,411	$ 124,909
Beginning Balance, Parent at Dec. 31, 2014	10,368,456	8,536,340	50,000	3,629	1,950,639	(172,152)
Preferred Shares [Abstract]
Partial redemption of 8.29% Series K Cumulative Redeemable	(9,820)		(9,820)
Common Share Issuance:
Conversion of OP Units into Common Shares		3,712		1			(3,713)
Exercise of share options		32,205		8
EQR's Employee Share Purchase Plan (ESPP)		1,927
Share-based employee compensation expense:
Restricted Shares		6,720		2
Share options		997
ESPP discount		412
Supplemental Executive Retirement Plan (SERP)		(2,307)
Change in market value of Redeemable Noncontrolling Interests - Operating Partnership	41,763	(41,763)
Adjustment for Noncontrolling Interests ownership in Operating Partnership		872					(872)
Net income attributable to controlling interests	182,522				182,522
Common Share distributions					(201,032)
Preferred Share distributions					(891)
Premium on redemption of Preferred Shares	(2,789)				(2,789)
Other comprehensive (loss) income – derivative instruments:
Unrealized holding (losses) arising during the period	(11,788)					(11,788)
Losses reclassified into earnings from other comprehensive income	(4,338)					4,338
Currency translation adjustments arising during the period	(420)					(420)
Issuance of restricted units to Noncontrolling Interests							1
Equity Compensation associated with Noncontrolling Interests							9,963
Net (income) attributable to Noncontrolling Interests - Operating Partnership	(7,059)						7,059
Distributions to Noncontrolling Interests							(7,913)	(2,891)
Change in carrying value	(630)						630
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	643							643
Ending Balance, Noncontrolling Interest at Mar. 31, 2015	342,227						219,566	122,661
Ending Balance, Parent at Mar. 31, 2015	$ 10,331,362	$ 8,539,115	$ 40,180	$ 3,640	$ 1,928,449	$ (180,022)