CONSOLIDATED STATEMENTS OF CASH FLOWS OF ERP OPERATING LIMITED PARTNERSHIP $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 1,009,708	$ 685,192	$ 628,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	831,083	785,725	743,749
Amortization of deferred financing costs	11,670	11,310	8,526
Amortization of above/below market lease intangibles	(71)	4,392	3,828
Amortization of discounts and premiums on debt	11,780	22,781	3,536
Amortization of deferred settlements on derivative instruments	21,176	18,440	18,847
Amortization of right-of-use assets	11,764
Impairment		702	1,693
Write-off of pursuit costs	5,529	4,450	3,106
(Income) loss from investments in unconsolidated entities	(65,945)	3,667	3,370
Distributions from unconsolidated entities – return on capital	2,621	2,492	2,632
Net (gain) loss on sales of real estate properties	(447,637)	(256,810)	(157,057)
Net (gain) loss on sales of land parcels	(2,044)	(987)	(19,167)
Net (gain) loss on debt extinguishment	13,647	22,110	12,258
Realized/unrealized (gain) loss on derivative instruments		50
Compensation paid with Company Common Shares	24,449	27,132	24,997
Other operating activities, net	287
Changes in assets and liabilities:
(Increase) decrease in other assets	6,278	4,097	(449)
Increase (decrease) in accounts payable and accrued expenses	5,116	(1,862)	11,532
Increase (decrease) in accrued interest payable	4,230	4,587	(2,911)
Increase (decrease) in lease liabilities	(2,269)
Increase (decrease) in other liabilities	13,382	16,578	(23,468)
Increase (decrease) in security deposits	2,804	2,249	2,385
Net cash provided by operating activities	1,456,984	1,356,295	1,265,788
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate – acquisitions	(1,518,878)	(708,092)	(466,394)
Investment in real estate – development/other	(195,692)	(154,431)	(276,382)
Capital expenditures to real estate	(178,423)	(188,501)	(202,607)
Non-real estate capital additions	(4,955)	(4,505)	(1,506)
Interest capitalized for real estate under development	(6,884)	(6,260)	(26,290)
Proceeds from disposition of real estate, net	1,064,619	691,526	384,583
Investments in unconsolidated entities	(9,604)	(6,571)	(6,034)
Distributions from unconsolidated entities – return of capital	78,262		334
Purchase of investment securities and other investments	(269)
Net cash provided by (used for) investing activities	(771,824)	(376,834)	(594,296)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt financing costs	(19,812)	(8,583)	(6,289)
Mortgage notes payable, net:
Proceeds	295,771	96,935
Lump sum payoffs	(743,021)	(1,347,939)	(493,420)
Scheduled principal repayments	(6,808)	(6,629)	(10,704)
Notes, net:
Proceeds	1,194,468	896,294	692,466
Lump sum payoffs	(1,050,000)		(497,975)
Line of credit and commercial paper:
Line of credit proceeds	6,010,000	3,805,000	1,845,000
Line of credit repayments	(5,990,000)	(3,805,000)	(1,845,000)
Commercial paper proceeds	15,944,800	14,030,926	5,066,509
Commercial paper repayments	(15,446,150)	(13,831,500)	(4,786,750)
Proceeds from (payments on) settlement of derivative instruments	(41,616)	18,118	1,295
Prepaid finance ground lease	(34,734)
Proceeds from Employee Share Purchase Plan (ESPP)	3,116	3,879	3,744
Proceeds from exercise of EQR options	77,785	30,655	31,596
Payment of offering costs	(991)	(27)	(51)
Other financing activities, net	(80)	(78)	(63)
Acquisition of Noncontrolling Interests – Partially Owned Properties		(13)
Contributions – Noncontrolling Interests – Partially Owned Properties	7,337	125	125
Contributions – Limited Partners	2	1
Distributions:
OP Units – General Partner	(831,111)	(782,122)	(739,375)
Preference Units	(3,090)	(3,863)	(3,091)
OP Units – Limited Partners	(29,615)	(28,226)	(27,291)
Noncontrolling Interests – Partially Owned Properties	(7,078)	(9,753)	(8,286)
Net cash provided by (used for) financing activities	(684,474)	(963,910)	(789,818)
Net increase (decrease) in cash and cash equivalents and restricted deposits	686	15,551	(118,326)
Cash and cash equivalents and restricted deposits, beginning of year	116,313	100,762	219,088
Cash and cash equivalents and restricted deposits, end of year	116,999	116,313	100,762
Cash and cash equivalents	45,753	47,442	50,647
Restricted deposits	71,246	68,871	50,115
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	342,048	358,156	360,273
Net cash paid (received) for income and other taxes	(585)	853	640
Amortization of deferred financing costs:
Investment in real estate, net	120
Other assets	2,987	2,412	2,412
Mortgage notes payable, net	3,934	4,792	2,493
Notes, net	4,869	4,106	3,621
Amortization of discounts and premiums on debt:
Mortgage notes payable, net	8,618	20,144	1,172
Notes, net	3,162	2,637	2,364
Amortization of deferred settlements on derivative instruments:
Other liabilities	(12)	(12)	(11)
Accumulated other comprehensive income	21,188	18,452	18,858
Write-off of pursuit costs:
Investment in real estate, net	5,451	4,364	2,965
Other assets	62	53	17
Accounts payable and accrued expenses	16	33	124
(Income) loss from investments in unconsolidated entities:
Investments in unconsolidated entities	(67,268)	2,304	1,955
Other liabilities	1,323	1,363	1,415
Realized/unrealized (gain) loss on derivative instruments:
Other assets	2,002	(14,977)	(4,582)
Notes, net	2,277	(680)	(3,454)
Other liabilities	29,486	10,533	1,597
Accumulated other comprehensive income	(33,765)	5,174	6,439
Investments in unconsolidated entities:
Investments in unconsolidated entities	(7,504)	(4,891)	(3,034)
Other liabilities	(2,100)	(1,680)	(3,000)
Debt financing costs:
Other assets	(6,909)	(145)
Mortgage notes payable, net	2,354	555
Notes, net	(10,549)	(7,883)	(6,289)
Right-of-use assets and lease liabilities initial measurement and reclassifications:
Right-of-use assets	(489,517)
Other assets	184,116
Lease liabilities	333,603
Other liabilities	28,202
Proceeds from (payments on) settlement of derivative instruments:
Other assets		18,118	1,295
Other liabilities	41,616
Mortgage Notes Payable, Net [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net gain (loss) on debt extinguishment	(3,381)	(22,110)	(12,258)
ERPOP [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	1,009,708	685,192	628,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	831,083	785,725	743,749
Amortization of deferred financing costs	11,670	11,310	8,526
Amortization of above/below market lease intangibles	(71)	4,392	3,828
Amortization of discounts and premiums on debt	11,780	22,781	3,536
Amortization of deferred settlements on derivative instruments	21,176	18,440	18,847
Amortization of right-of-use assets	11,764
Impairment		702	1,693
Write-off of pursuit costs	5,529	4,450	3,106
(Income) loss from investments in unconsolidated entities	(65,945)	3,667	3,370
Distributions from unconsolidated entities – return on capital	2,621	2,492	2,632
Net (gain) loss on sales of real estate properties	(447,637)	(256,810)	(157,057)
Net (gain) loss on sales of land parcels	(2,044)	(987)	(19,167)
Net (gain) loss on debt extinguishment	13,647	22,110	12,258
Realized/unrealized (gain) loss on derivative instruments		50
Compensation paid with Company Common Shares	24,449	27,132	24,997
Other operating activities, net	287
Changes in assets and liabilities:
(Increase) decrease in other assets	6,278	4,097	(449)
Increase (decrease) in accounts payable and accrued expenses	5,116	(1,862)	11,532
Increase (decrease) in accrued interest payable	4,230	4,587	(2,911)
Increase (decrease) in lease liabilities	(2,269)
Increase (decrease) in other liabilities	13,382	16,578	(23,468)
Increase (decrease) in security deposits	2,804	2,249	2,385
Net cash provided by operating activities	1,456,984	1,356,295	1,265,788
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate – acquisitions	(1,518,878)	(708,092)	(466,394)
Investment in real estate – development/other	(195,692)	(154,431)	(276,382)
Capital expenditures to real estate	(178,423)	(188,501)	(202,607)
Non-real estate capital additions	(4,955)	(4,505)	(1,506)
Interest capitalized for real estate under development	(6,884)	(6,260)	(26,290)
Proceeds from disposition of real estate, net	1,064,619	691,526	384,583
Investments in unconsolidated entities	(9,604)	(6,571)	(6,034)
Distributions from unconsolidated entities – return of capital	78,262		334
Purchase of investment securities and other investments	(269)
Net cash provided by (used for) investing activities	(771,824)	(376,834)	(594,296)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt financing costs	(19,812)	(8,583)	(6,289)
Net gain (loss) on debt extinguishment	(10,266)
Mortgage notes payable, net:
Proceeds	295,771	96,935
Lump sum payoffs	(743,021)	(1,347,939)	(493,420)
Scheduled principal repayments	(6,808)	(6,629)	(10,704)
Notes, net:
Proceeds	1,194,468	896,294	692,466
Lump sum payoffs	(1,050,000)		(497,975)
Line of credit and commercial paper:
Line of credit proceeds	6,010,000	3,805,000	1,845,000
Line of credit repayments	(5,990,000)	(3,805,000)	(1,845,000)
Commercial paper proceeds	15,944,800	14,030,926	5,066,509
Commercial paper repayments	(15,446,150)	(13,831,500)	(4,786,750)
Proceeds from (payments on) settlement of derivative instruments	(41,616)	18,118	1,295
Prepaid finance ground lease	(34,734)
Proceeds from Employee Share Purchase Plan (ESPP)	3,116	3,879	3,744
Proceeds from exercise of EQR options	77,785	30,655	31,596
Payment of offering costs	(991)	(27)	(51)
Other financing activities, net	(80)	(78)	(63)
Acquisition of Noncontrolling Interests – Partially Owned Properties		(13)
Contributions – Noncontrolling Interests – Partially Owned Properties	7,337	125	125
Contributions – Limited Partners	2	1
Distributions:
OP Units – General Partner	(831,111)	(782,122)	(739,375)
Preference Units	(3,090)	(3,863)	(3,091)
OP Units – Limited Partners	(29,615)	(28,226)	(27,291)
Noncontrolling Interests – Partially Owned Properties	(7,078)	(9,753)	(8,286)
Net cash provided by (used for) financing activities	(684,474)	(963,910)	(789,818)
Net increase (decrease) in cash and cash equivalents and restricted deposits	686	15,551	(118,326)
Cash and cash equivalents and restricted deposits, beginning of year	116,313	100,762	219,088
Cash and cash equivalents and restricted deposits, end of year	116,999	116,313	100,762
Cash and cash equivalents	45,753	47,442	50,647
Restricted deposits	71,246	68,871	50,115
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	342,048	358,156	360,273
Net cash paid (received) for income and other taxes	(585)	853	640
Amortization of deferred financing costs:
Investment in real estate, net	(120)
Other assets	2,987	2,412	2,412
Mortgage notes payable, net	3,934	4,792	2,493
Notes, net	4,869	4,106	3,621
Amortization of discounts and premiums on debt:
Mortgage notes payable, net	8,618	20,144	1,172
Notes, net	3,162	2,637	2,364
Amortization of deferred settlements on derivative instruments:
Other liabilities	(12)	(12)	(11)
Accumulated other comprehensive income	21,188	18,452	18,858
Write-off of pursuit costs:
Investment in real estate, net	5,451	4,364	2,965
Other assets	62	53	17
Accounts payable and accrued expenses	16	33	124
(Income) loss from investments in unconsolidated entities:
Investments in unconsolidated entities	(67,268)	2,304	1,955
Other liabilities	1,323	1,363	1,415
Realized/unrealized (gain) loss on derivative instruments:
Other assets	2,002	(14,977)	(4,582)
Notes, net	2,277	(680)	(3,454)
Other liabilities	29,486	10,533	1,597
Accumulated other comprehensive income	(33,765)	5,174	6,439
Investments in unconsolidated entities:
Investments in unconsolidated entities	(7,504)	(4,891)	(3,034)
Other liabilities	(2,100)	(1,680)	(3,000)
Debt financing costs:
Other assets	(6,909)	(145)
Mortgage notes payable, net	(2,354)	(555)
Notes, net	(10,549)	(7,883)	(6,289)
Right-of-use assets and lease liabilities initial measurement and reclassifications:
Right-of-use assets	(489,517)
Other assets	184,116
Lease liabilities	333,603
Other liabilities	(28,202)
Proceeds from (payments on) settlement of derivative instruments:
Other assets		18,118	1,295
Other liabilities	(41,616)
ERPOP [Member] | Mortgage Notes Payable, Net [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net gain (loss) on debt extinguishment	$ (3,381)	$ (22,110)	$ (12,258)