Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 289,159	$ 348,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	359,287	350,893
Amortization of discount on marketable securities	(12,949)	(11,128)
Amortization of (premium) discount and debt financing costs, net	(1,958)	(5,132)
Gain on sale of marketable securities and other investments	(669)	(1,650)
Unrealized gain on equity securities recognized through income	(426)	0
Company's share of gain on the sales of co-investments	0	(10,058)
Earnings from co-investments	(64,611)	(30,876)
Operating distributions from co-investments	80,232	47,702
Accrued interest from notes and other receivables	(4,016)	(2,738)
Gain on the sale of real estate and land	(22,244)	(26,423)
Equity-based compensation	7,209	4,894
Gain on remeasurement of co-investment	0	(88,641)
Changes in operating assets and liabilities:
Prepaid expenses, receivables and other assets	(4,044)	(2,844)
Accounts payable and accrued liabilities	55,469	50,788
Other liabilities	698	399
Net cash provided by operating activities	681,137	623,567
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures	(7,807)	(200,028)
Redevelopment	(54,656)	(50,642)
Development acquisitions of and additions to real estate under development	(131,867)	(92,936)
Capital expenditures on rental properties	(54,890)	(48,735)
Investments in notes receivable	0	(76,961)
Collections of notes receivable	29,500	0
Proceeds from insurance for property losses	1,237	648
Proceeds from dispositions of real estate	130,730	132,039
Contributions to co-investments	(100,202)	(231,552)
Changes in refundable deposits	(3,804)	2,594
Purchases of marketable securities	(29,130)	(65,668)
Sales and maturities of marketable securities	22,501	33,377
Non-operating distributions from co-investments	62,564	112,572
Net cash used in investing activities	(135,824)	(485,292)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	298,773	597,981
Payments on unsecured debt and mortgage notes	(162,317)	(460,040)
Proceeds from lines of credit	454,170	564,833
Repayments of lines of credit	(633,170)	(687,224)
Retirement of common stock	(3,774)	0
Additions to deferred charges	(4,093)	(4,108)
Net proceeds from issuance of common stock	(483)	80,377
Net proceeds from stock options exercised	2,751	24,079
Payments related to tax withholding for share-based compensation	(23)	(118)
Distributions to noncontrolling interest	(22,137)	(20,405)
Redemption of noncontrolling interest	(157)	(4,849)
Redemption of redeemable noncontrolling interest	(43)	(720)
Common and preferred stock dividends paid	(361,310)	(335,110)
Net cash used in financing activities	(431,813)	(245,304)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	113,500	(107,029)
Unrestricted and restricted cash and cash equivalents at beginning of period	61,126	170,302
Unrestricted and restricted cash and cash equivalents at end of period	174,626	63,273
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $13.3 million and $10.0 million capitalized in 2018 and 2017, respectively)	146,039	148,742
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT units in connection with acquisition of real estate	0	22,506
Transfers between real estate under development to rental properties, net	99,547	2,195
Transfer from real estate under development to co-investments	640	4,122
Reclassifications to redeemable noncontrolling interest from additional paid in capital and noncontrolling interest	2,253	903
Redemption of redeemable noncontrolling interest via reduction of note receivable	4,751	0
Debt assumed in connection with acquisition	0	51,882
Repayment of mortgage note from new financing proceeds	52,000	0
Essex Portfolio, L.P. [Member]
Cash flows from operating activities:
Net income	289,159	348,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	359,287	350,893
Amortization of discount on marketable securities	(12,949)	(11,128)
Amortization of (premium) discount and debt financing costs, net	(1,958)	(5,132)
Gain on sale of marketable securities and other investments	(669)	(1,650)
Unrealized gain on equity securities recognized through income	(426)	0
Company's share of gain on the sales of co-investments	0	(10,058)
Earnings from co-investments	(64,611)	(30,876)
Operating distributions from co-investments	80,232	47,702
Accrued interest from notes and other receivables	(4,016)	(2,738)
Gain on the sale of real estate and land	(22,244)	(26,423)
Equity-based compensation	7,209	4,894
Gain on remeasurement of co-investment	0	(88,641)
Changes in operating assets and liabilities:
Prepaid expenses, receivables and other assets	(4,044)	(2,844)
Accounts payable and accrued liabilities	55,469	50,788
Other liabilities	698	399
Net cash provided by operating activities	681,137	623,567
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures	(7,807)	(200,028)
Redevelopment	(54,656)	(50,642)
Development acquisitions of and additions to real estate under development	(131,867)	(92,936)
Capital expenditures on rental properties	(54,890)	(48,735)
Investments in notes receivable	0	(76,961)
Collections of notes receivable	29,500	0
Proceeds from insurance for property losses	1,237	648
Proceeds from dispositions of real estate	130,730	132,039
Contributions to co-investments	(100,202)	(231,552)
Changes in refundable deposits	(3,804)	2,594
Purchases of marketable securities	(29,130)	(65,668)
Sales and maturities of marketable securities	22,501	33,377
Non-operating distributions from co-investments	62,564	112,572
Net cash used in investing activities	(135,824)	(485,292)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	298,773	597,981
Payments on unsecured debt and mortgage notes	(162,317)	(460,040)
Proceeds from lines of credit	454,170	564,833
Repayments of lines of credit	(633,170)	(687,224)
Retirement of common stock	(3,774)	0
Additions to deferred charges	(4,093)	(4,108)
Net proceeds from issuance of common stock	(483)	80,377
Net proceeds from stock options exercised	2,751	24,079
Payments related to tax withholding for share-based compensation	(23)	(118)
Distributions to noncontrolling interest	(6,615)	(5,568)
Redemption of noncontrolling interest	(157)	(4,849)
Redemption of redeemable noncontrolling interest	(43)	(720)
Common and preferred stock dividends paid	(376,832)	(349,947)
Net cash used in financing activities	(431,813)	(245,304)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	113,500	(107,029)
Unrestricted and restricted cash and cash equivalents at beginning of period	61,126	170,302
Unrestricted and restricted cash and cash equivalents at end of period	174,626	63,273
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $13.3 million and $10.0 million capitalized in 2018 and 2017, respectively)	146,039	148,742
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT units in connection with acquisition of real estate	0	22,506
Transfers between real estate under development to rental properties, net	99,547	2,195
Transfer from real estate under development to co-investments	640	4,122
Reclassifications to redeemable noncontrolling interest from additional paid in capital and noncontrolling interest	2,253	903
Redemption of redeemable noncontrolling interest via reduction of note receivable	4,571	0
Debt assumed in connection with acquisition	0	51,882
Repayment of mortgage note from new financing proceeds	$ 52,000	$ 0