CONSOLIDATED STATEMENTS OF CASH FLOWS OF ERP OPERATING LIMITED PARTNERSHIP (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 658,683,000	$ 1,905,353,000	$ 881,204,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	758,861,000	1,013,353,000	684,992,000
Amortization of deferred financing costs	11,088,000	22,425,000	21,435,000
Amortization of above/below market leases	3,222,000	898,000	0
Amortization of discounts and premiums on debt	(13,520,000)	(156,439,000)	(8,181,000)
Amortization of deferred settlements on derivative instruments	16,334,000	19,607,000	14,144,000
Write-off of pursuit costs	3,607,000	5,184,000	9,056,000
Loss from investments in unconsolidated entities	7,952,000	58,156,000	14,000
Distributions from unconsolidated entities - return on capital	5,570,000	2,481,000	575,000
Net (gain) on sales of investment securities	(57,000)	(4,203,000)	0
Net (gain) on sales of real estate properties	(212,685,000)	0	0
Net (gain) on sales of land parcels	(5,277,000)	(12,227,000)	0
Net (gain) on sales of discontinued operations	(179,000)	(2,036,505,000)	(548,278,000)
Unrealized (gain) loss on derivative instruments	(60,000)	70,000	(1,000)
Compensation paid with Company Common Shares	27,543,000	35,474,000	24,832,000
Changes in assets and liabilities:
(Increase) decrease in deposits - restricted	(1,740,000)	3,684,000	(4,091,000)
Decrease in mortgage deposits	1,452,000	1,813,000	176,000
Decrease (increase) in other assets	21,773,000	3,742,000	(20,411,000)
Increase (decrease) in accounts payable and accrued expenses	17,797,000	6,229,000	(2,102,000)
Increase (decrease) in accrued interest payable	11,231,000	(9,219,000)	(11,898,000)
Increase in other liabilities	8,437,000	15,401,000	2,987,000
Increase (decrease) in security deposits	4,041,000	(6,361,000)	1,702,000
Net cash provided by operating activities	1,324,073,000	868,916,000	1,046,155,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of Archstone, net of cash acquired	0	(4,000,875,000)	0
Investment in real estate - acquisitions	(469,989,000)	(108,308,000)	(843,976,000)
Investment in real estate - development/other	(530,387,000)	(377,442,000)	(180,409,000)
Capital expenditures to real estate	(185,957,000)	(135,816,000)	(152,828,000)
Non-real estate capital additions	(5,286,000)	(4,134,000)	(8,821,000)
Interest capitalized for real estate and unconsolidated entities under development	(52,782,000)	(47,321,000)	(22,509,000)
Proceeds from disposition of real estate, net	522,647,000	4,551,454,000	1,049,219,000
Investments in unconsolidated entities	(15,768,000)	(66,471,000)	(5,291,000)
Distributions from unconsolidated entities - return of capital	103,793,000	25,471,000	0
Proceeds from sale of investment securities	57,000	4,878,000	0
Decrease (increase) in deposits on real estate acquisitions and investments, net	33,004,000	143,694,000	(97,984,000)
Decrease in mortgage deposits	798,000	7,893,000	1,444,000
Consolidation of previously unconsolidated properties	(44,796,000)	0	0
Net cash (used for) investing activities	(644,666,000)	(6,977,000)	(261,155,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt financing costs	(10,982,000)	(16,526,000)	(21,209,000)
Mortgage deposits	(7,699,000)	(5,631,000)	(57,000)
Mortgage notes payable:
Proceeds	0	902,886,000	26,495,000
Restricted cash	0	0	2,370,000
Lump sum payoffs	(88,788,000)	(2,532,682,000)	(350,247,000)
Scheduled principal repayments	(11,869,000)	(12,658,000)	(14,088,000)
Notes, net:
Proceeds	1,194,277,000	1,245,550,000	0
Lump sum payoffs	(1,250,000,000)	(400,000,000)	(975,991,000)
Lines of credit:
Proceeds	7,167,000,000	9,832,000,000	5,876,000,000
Repayments	(6,949,000,000)	(9,717,000,000)	(5,876,000,000)
(Payments on) settlement of derivative instruments	(758,000)	(44,063,000)	0
Proceeds from EQR's Employee Share Purchase Plan (ESPP)	3,392,000	3,401,000	5,399,000
Proceeds from exercise of EQR options	82,573,000	17,252,000	49,039,000
OP units repurchased and retired	(1,777,000)	0	0
Redemption of Preference Units	0	0	(150,000,000)
Premium on redemption of Preference Units	0	0	(23,000)
Payment of offering costs	(41,000)	(1,047,000)	(39,359,000)
Other financing activities, net	(49,000)	(48,000)	(48,000)
Acquisition Noncontrolling Interests - Partially Owned Properties	(5,501,000)	0	(13,000)
Contributions - Noncontrolling Interests - Partially Owned Properties	5,684,000	27,660,000	8,221,000
Contributions - Limited Partners	3,000	5,000	5,000
Distributions:
Net cash (used for) financing activities	(692,861,000)	(1,420,995,000)	(556,331,000)
Net (decrease) increase in cash and cash equivalents	(13,454,000)	(559,056,000)	228,669,000
Cash and cash equivalents, beginning of year	53,534,000	612,590,000	383,921,000
Cash and cash equivalents, end of year	40,080,000	53,534,000	612,590,000
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	443,125,000	722,963,000	464,785,000
Net cash paid for income and other taxes	1,517,000	1,152,000	673,000
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	28,910,000	0	137,644,000
Valuation of OP Units issued	0	0	66,606,000
Amortization of deferred financing costs:
Investment in real estate, net	0	(152,000)	0
Deferred financing costs, net	11,088,000	22,577,000	21,435,000
Amortization of discounts and premiums on debt:
Mortgage notes payable	(15,904,000)	(158,625,000)	(10,333,000)
Notes, net	2,384,000	2,186,000	2,152,000
Amortization of deferred settlements on derivative instruments:
Other liabilities	(534,000)	(534,000)	(534,000)
Accumulated other comprehensive income	16,868,000	20,141,000	14,678,000
Loss From Investments In Unconsolidated Entities:
Investments in unconsolidated entities	4,610,000	53,066,000	14,000
Other liabilities	3,342,000	5,090,000	0
Distributions from unconsolidated entities return on capital:
Investments in unconsolidated entities	5,360,000	2,448,000	575,000
Other liabilities	210,000	33,000	0
Unrealized (gain) loss on derivative instruments:
Other assets	10,160,000	(17,139,000)	7,448,000
Mortgage notes payable	0	0	(2,589,000)
Notes, net	1,597,000	(1,523,000)	(4,860,000)
Other liabilities	21,489,000	(39,000)	11,772,000
Accumulated other comprehensive income	(33,306,000)	18,771,000	(11,772,000)
Acquisition of Archstone, net of cash acquired:
Investment in real estate, net	39,929,000	(8,687,355,000)	0
Investments in unconsolidated entities	(33,993,000)	(225,568,000)	0
Deposits - restricted	0	(528,000)	0
Escrow deposits - mortgage	0	(37,582,000)	0
Deferred financing costs, net	0	(25,780,000)	0
Other assets	(2,586,000)	(215,622,000)	0
Mortgage notes payable	0	3,076,876,000	0
Accounts payable and accrued expenses	(146,000)	16,984,000	0
Accrued interest payable	0	11,305,000	0
Other liabilities	(3,204,000)	117,299,000	0
Security deposits	0	10,965,000	0
Issuance of OP Units	0	1,929,868,000	0
Noncontrolling Interests - Partially Owned Properties	0	28,263,000	0
Interest capitalized for real estate and unconsolidated entities under development:
Investment in real estate, net	(52,717,000)	(45,533,000)	(21,661,000)
Investments in unconsolidated entities	(65,000)	(1,788,000)	(848,000)
Investments in unconsolidated entities:
Investments in unconsolidated entities	(6,318,000)	(13,656,000)	(5,291,000)
Other liabilities	(9,450,000)	(52,815,000)	0
Consolidation of previously unconsolidated properties:
Investment in real estate, net	469,989,000	108,308,000	843,976,000
Investments in unconsolidated entities	15,768,000	66,471,000	5,291,000
Accounts payable and accrued expenses	17,797,000	6,229,000	(2,102,000)
(Payments on) settlement of derivative instruments:
Other assets	6,623,000	(50,000)	0
Other liabilities	(7,381,000)	(44,013,000)	0
Other:
Receivable on sale of OP Units	0	0	28,457,000
Foreign currency translation adjustments	552,000	(613,000)	0
OPERATING PARTNERSHIP
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	658,683,000	1,905,353,000	881,204,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	758,861,000	1,013,353,000	684,992,000
Amortization of deferred financing costs	11,088,000	22,425,000	21,435,000
Amortization of above/below market leases	3,222,000	898,000	0
Amortization of discounts and premiums on debt	(13,520,000)	(156,439,000)	(8,181,000)
Amortization of deferred settlements on derivative instruments	16,334,000	19,607,000	14,144,000
Write-off of pursuit costs	3,607,000	5,184,000	9,056,000
Loss from investments in unconsolidated entities	7,952,000	58,156,000	14,000
Distributions from unconsolidated entities - return on capital	5,570,000	2,481,000	575,000
Net (gain) on sales of investment securities	(57,000)	(4,203,000)	0
Net (gain) on sales of real estate properties	(212,685,000)	0	0
Net (gain) on sales of land parcels	(5,277,000)	(12,227,000)	0
Net (gain) on sales of discontinued operations	(179,000)	(2,036,505,000)	(548,278,000)
Unrealized (gain) loss on derivative instruments	(60,000)	70,000	(1,000)
Compensation paid with Company Common Shares	27,543,000	35,474,000	24,832,000
Changes in assets and liabilities:
(Increase) decrease in deposits - restricted	(1,740,000)	3,684,000	(4,091,000)
Decrease in mortgage deposits	1,452,000	1,813,000	176,000
Decrease (increase) in other assets	21,773,000	3,742,000	(20,411,000)
Increase (decrease) in accounts payable and accrued expenses	17,797,000	6,229,000	(2,102,000)
Increase (decrease) in accrued interest payable	11,231,000	(9,219,000)	(11,898,000)
Increase in other liabilities	8,437,000	15,401,000	2,987,000
Increase (decrease) in security deposits	4,041,000	(6,361,000)	1,702,000
Net cash provided by operating activities	1,324,073,000	868,916,000	1,046,155,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of Archstone, net of cash acquired	0	(4,000,875,000)	0
Investment in real estate - acquisitions	(469,989,000)	(108,308,000)	(843,976,000)
Investment in real estate - development/other	(530,387,000)	(377,442,000)	(180,409,000)
Capital expenditures to real estate	(185,957,000)	(135,816,000)	(152,828,000)
Non-real estate capital additions	(5,286,000)	(4,134,000)	(8,821,000)
Interest capitalized for real estate and unconsolidated entities under development	(52,782,000)	(47,321,000)	(22,509,000)
Proceeds from disposition of real estate, net	522,647,000	4,551,454,000	1,049,219,000
Investments in unconsolidated entities	(15,768,000)	(66,471,000)	(5,291,000)
Distributions from unconsolidated entities - return of capital	103,793,000	25,471,000	0
Proceeds from sale of investment securities	57,000	4,878,000	0
Decrease (increase) in deposits on real estate acquisitions and investments, net	33,004,000	143,694,000	(97,984,000)
Decrease in mortgage deposits	798,000	7,893,000	1,444,000
Consolidation of previously unconsolidated properties	(44,796,000)	0	0
Net cash (used for) investing activities	(644,666,000)	(6,977,000)	(261,155,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt financing costs	(10,982,000)	(16,526,000)	(21,209,000)
Mortgage deposits	(7,699,000)	(5,631,000)	(57,000)
Mortgage notes payable:
Proceeds	0	902,886,000	26,495,000
Restricted cash	0	0	2,370,000
Lump sum payoffs	(88,788,000)	(2,532,682,000)	(350,247,000)
Scheduled principal repayments	(11,869,000)	(12,658,000)	(14,088,000)
Notes, net:
Proceeds	1,194,277,000	1,245,550,000	0
Lump sum payoffs	(1,250,000,000)	(400,000,000)	(975,991,000)
Lines of credit:
Proceeds	7,167,000,000	9,832,000,000	5,876,000,000
Repayments	(6,949,000,000)	(9,717,000,000)	(5,876,000,000)
(Payments on) settlement of derivative instruments	(758,000)	(44,063,000)	0
Proceeds from sale of OP Units	0	0	1,417,040,000
Proceeds from EQR's Employee Share Purchase Plan (ESPP)	3,392,000	3,401,000	5,399,000
Proceeds from exercise of EQR options	82,573,000	17,252,000	49,039,000
OP units repurchased and retired	(1,777,000)	0	0
Redemption of Preference Units	0	0	(150,000,000)
Premium on redemption of Preference Units	0	0	(23,000)
Payment of offering costs	(41,000)	(1,047,000)	(39,359,000)
Other financing activities, net	(49,000)	(48,000)	(48,000)
Acquisition Noncontrolling Interests - Partially Owned Properties	(5,501,000)	0	(13,000)
Contributions - Noncontrolling Interests - Partially Owned Properties	5,684,000	27,660,000	8,221,000
Contributions - Limited Partners	3,000	5,000	5,000
Distributions:
OP Units - General Partner	(776,659,000)	(681,610,000)	(473,451,000)
Preference Units	(4,145,000)	(4,145,000)	(13,416,000)
OP Units - Limited Partners	(30,744,000)	(27,897,000)	(21,915,000)
Noncontrolling Interests - Partially Owned Properties	(7,778,000)	(6,442,000)	(5,083,000)
Net cash (used for) financing activities	(692,861,000)	(1,420,995,000)	(556,331,000)
Net (decrease) increase in cash and cash equivalents	(13,454,000)	(559,056,000)	228,669,000
Cash and cash equivalents, beginning of year	53,534,000	612,590,000	383,921,000
Cash and cash equivalents, end of year	40,080,000	53,534,000	612,590,000
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	443,125,000	722,963,000	464,785,000
Net cash paid for income and other taxes	1,517,000	1,152,000	673,000
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	28,910,000	0	137,644,000
Valuation of OP Units issued	0	0	66,606,000
Amortization of deferred financing costs:
Investment in real estate, net	0	(152,000)	0
Deferred financing costs, net	11,088,000	22,577,000	21,435,000
Amortization of discounts and premiums on debt:
Mortgage notes payable	(15,904,000)	(158,625,000)	(10,333,000)
Notes, net	2,384,000	2,186,000	2,152,000
Amortization of deferred settlements on derivative instruments:
Other liabilities	(534,000)	(534,000)	(534,000)
Accumulated other comprehensive income	16,868,000	20,141,000	14,678,000
Loss From Investments In Unconsolidated Entities:
Investments in unconsolidated entities	4,610,000	53,066,000	14,000
Other liabilities	3,342,000	5,090,000	0
Distributions from unconsolidated entities return on capital:
Investments in unconsolidated entities	5,360,000	2,448,000	575,000
Other liabilities	210,000	33,000	0
Unrealized (gain) loss on derivative instruments:
Other assets	10,160,000	(17,139,000)	7,448,000
Mortgage notes payable	0	0	(2,589,000)
Notes, net	1,597,000	(1,523,000)	(4,860,000)
Other liabilities	21,489,000	(39,000)	11,772,000
Accumulated other comprehensive income	(33,306,000)	18,771,000	(11,772,000)
Acquisition of Archstone, net of cash acquired:
Investment in real estate, net	39,929,000	(8,687,355,000)	0
Investments in unconsolidated entities	(33,993,000)	(225,568,000)	0
Deposits - restricted	0	(528,000)	0
Escrow deposits - mortgage	0	(37,582,000)	0
Deferred financing costs, net	0	(25,780,000)	0
Other assets	(2,586,000)	(215,622,000)	0
Mortgage notes payable	0	3,076,876,000	0
Accounts payable and accrued expenses	(146,000)	16,984,000	0
Accrued interest payable	0	11,305,000	0
Other liabilities	(3,204,000)	117,299,000	0
Security deposits	0	10,965,000	0
Issuance of OP Units	0	1,929,868,000	0
Noncontrolling Interests - Partially Owned Properties	0	28,263,000	0
Interest capitalized for real estate and unconsolidated entities under development:
Investment in real estate, net	(52,717,000)	(45,533,000)	(21,661,000)
Investments in unconsolidated entities	(65,000)	(1,788,000)	(848,000)
Investments in unconsolidated entities:
Investments in unconsolidated entities	(6,318,000)	(13,656,000)	(5,291,000)
Other liabilities	(9,450,000)	(52,815,000)	0
Consolidation of previously unconsolidated properties:
Investment in real estate, net	469,989,000	108,308,000	843,976,000
Investments in unconsolidated entities	15,768,000	66,471,000	5,291,000
Accounts payable and accrued expenses	17,797,000	6,229,000	(2,102,000)
(Payments on) settlement of derivative instruments:
Other assets	6,623,000	(50,000)	0
Other liabilities	(7,381,000)	(44,013,000)	0
Other:
Receivable on sale of OP Units	0	0	28,457,000
Foreign currency translation adjustments	552,000	(613,000)	0
Consolidated Development Projects Held for and or Under Development [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	(70,000)
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from investments in unconsolidated entities	0
Distributions:
Cash and cash equivalents, end of year	0
Parc on Powell (fka Parkside at Emeryville) [Member]
Changes in assets and liabilities:
Increase (decrease) in accounts payable and accrued expenses	1,987,000	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate - acquisitions	64,319,000	0	0
Investments in unconsolidated entities	847,000	0	0
Consolidation of previously unconsolidated properties:
Investment in real estate, net	(64,319,000)	0	0
Investments in unconsolidated entities	(847,000)	0	0
Accounts payable and accrued expenses	1,987,000	0	0
Other Liabilities	18,383,000	0	0
Parc on Powell (fka Parkside at Emeryville) [Member] | OPERATING PARTNERSHIP
Changes in assets and liabilities:
Increase (decrease) in accounts payable and accrued expenses	1,987,000	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate - acquisitions	64,319,000	0	0
Investments in unconsolidated entities	847,000	0	0
Consolidation of previously unconsolidated properties:
Investment in real estate, net	(64,319,000)	0	0
Investments in unconsolidated entities	(847,000)	0	0
Accounts payable and accrued expenses	1,987,000	0	0
Other Liabilities	$ 18,383,000	$ 0	$ 0