CONSOLIDATED STATEMENTS OF OPERATIONS OF ERP OPERATING LIMITED PARTNERSHIP (Unaudited) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
REVENUES
Rental income	$ 537,002,000	$ 444,384,000
Fee and asset management	2,160,000	2,064,000
Total revenues	539,162,000	446,448,000
EXPENSES
Property and maintenance	107,083,000	92,952,000
Real estate taxes and insurance	68,647,000	52,440,000
Property management	22,489,000	23,339,000
Fee and asset management	1,646,000	1,307,000
Depreciation	205,272,000	148,246,000
General and administrative	16,496,000	13,688,000
Total expenses	421,633,000	331,972,000
Operating income	117,529,000	114,476,000
Interest and other income	256,000	169,000
Other expenses	(2,564,000)	(5,807,000)
Merger Expenses	19,092,000	1,149,000
Interest:
Expense incurred, net	(195,685,000)	(118,011,000)
Amortization of deferred financing costs	(7,023,000)	(2,934,000)
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(106,579,000)	(13,256,000)
Income and other tax (expense) benefit	(407,000)	(170,000)
Loss from investments in unconsolidated entities	(355,000)	0
Income Loss From Equity Method Investments Merger Expenses	(46,011,000)	0
Income from continuing operations	(153,352,000)	(13,426,000)
Discontinued operations, net	1,214,386,000	165,593,000
Net income	1,061,034,000	152,167,000
Net (income) attributable to Noncontrolling Interests - Partially Owned Properties	(25,000)	(450,000)
Net income attributable to controlling interests	1,017,686,000	145,299,000
Earnings per Unit - basic:
Income (loss) from continuing operations available to Units	$ (0.439)	$ (0.055)
Net income available to Units	$ 3.012	$ 0.475
Earnings per Unit - diluted:
Income (loss) from continuing operations available to Units	$ (0.439)	$ (0.055)
Net income available to Units	$ 3.012	$ 0.475
OPERATING PARTNERSHIP
REVENUES
Rental income	537,002,000	444,384,000
Fee and asset management	2,160,000	2,064,000
Total revenues	539,162,000	446,448,000
EXPENSES
Property and maintenance	107,083,000	92,952,000
Real estate taxes and insurance	68,647,000	52,440,000
Property management	22,489,000	23,339,000
Fee and asset management	1,646,000	1,307,000
Depreciation	205,272,000	148,246,000
General and administrative	16,496,000	13,688,000
Total expenses	421,633,000	331,972,000
Operating income	117,529,000	114,476,000
Interest and other income	256,000	169,000
Other expenses	(2,564,000)	(5,807,000)
Merger Expenses	(19,092,000)	(1,149,000)
Interest:
Expense incurred, net	(195,685,000)	(118,011,000)
Amortization of deferred financing costs	(7,023,000)	(2,934,000)
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(106,579,000)	(13,256,000)
Income and other tax (expense) benefit	(407,000)	(170,000)
Loss from investments in unconsolidated entities	(355,000)	0
Income Loss From Equity Method Investments Merger Expenses	(46,011,000)	0
Income from continuing operations	(153,352,000)	(13,426,000)
Discontinued operations, net	1,214,386,000	165,593,000
Net income	1,061,034,000	152,167,000
Net (income) attributable to Noncontrolling Interests - Partially Owned Properties	(25,000)	(450,000)
Net income attributable to controlling interests	1,061,009,000	151,717,000
ALLOCATION OF NET INCOME:
Preference Units	1,036,000	3,466,000
General Partner	1,016,650,000	141,833,000
Limited Partners	43,323,000	6,418,000
Net income available to Units	$ 1,059,973,000	$ 148,251,000
Earnings per Unit - basic:
Income (loss) from continuing operations available to Units	$ (0.440)	$ (0.060)
Net income available to Units	$ 3.012	$ 0.470
Weighted average Units outstanding	351,255	312,011
Earnings per Unit - diluted:
Income (loss) from continuing operations available to Units	$ (0.440)	$ (0.060)
Net income available to Units	$ 3.010	$ 0.470
Weighted average Units outstanding	351,255	312,011
Distributions declared per Unit outstanding	$ 0.40	$ 0.3375