CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME OF ERP OPERATING LIMITED PARTNERSHIP (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Comprehensive income:
Net income	$ 1,061,034	$ 152,167
Other comprehensive (loss) - derivative instruments:
Unrealized holding (losses) arising during the period	2,814	3,218
Losses reclassified into earnings from other comprehensive income	8,272	3,563
Other comprehensive income - other instruments:
Unrealized holding gains arising during the period	427	(36)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(873)	0
Other Comprehensive (loss)	10,640	6,745
Comprehensive income	1,071,674	158,912
Comprehensive (income), Net of Tax, Attributable to Noncontrolling Interest	(43,348)	(6,868)
Comprehensive income attributable to controlling interests	1,028,326	152,044
OPERATING PARTNERSHIP
Comprehensive income:
Net income	1,061,034	152,167
Other comprehensive (loss) - derivative instruments:
Unrealized holding (losses) arising during the period	2,814	3,218
Losses reclassified into earnings from other comprehensive income	(8,272)	(3,563)
Other comprehensive income - other instruments:
Unrealized holding gains arising during the period	427	(36)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(873)	0
Other Comprehensive (loss)	10,640	6,745
Comprehensive income	1,071,674	158,912
Comprehensive (income), Net of Tax, Attributable to Noncontrolling Interest	(25)	(450)
Comprehensive income attributable to controlling interests	$ 1,071,649	$ 158,462