Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 328,765	$ 125,505
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	131,559	120,568
Amortization of discount on marketable securities	(2,394)	(5,311)
Amortization of discount and debt financing costs, net	2,297	529
Loss on sale of marketable securities	13	58
Provision for credit losses	(50)
Unrealized (gain) loss on equity securities recognized through income	8,696	(4,510)
Earnings from co-investments	(21,297)	(16,276)
Operating distributions from co-investments	19,388	17,804
Accrued interest from notes and other receivables	(355)	(1,424)
Equity-based compensation	1,405	2,068
Gain on early retirement of debt, net	(321)	(1,336)
Gain on remeasurement of co-investment	(234,694)	(31,535)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets	(172)	(4,730)
Accounts payable, accrued liabilities, and operating lease liabilities	32,808	53,895
Other liabilities	1,278	454
Net cash provided by operating activities	266,926	255,759
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired	(458,302)	(44,984)
Redevelopment	(18,296)	(14,157)
Development acquisitions of and additions to real estate under development	(25,681)	(39,306)
Capital expenditures on rental properties	(17,151)	(17,075)
Collections of notes and other receivables	98,711	2,500
Proceeds from insurance for property losses	457	1,583
Contributions to co-investments	(21,905)	(126,248)
Changes in refundable deposits	96	5
Purchases of marketable securities	(10,731)	(8,413)
Sales and maturities of marketable securities	165	16,847
Non-operating distributions from co-investments	7,000	10,000
Net cash used in investing activities	(445,637)	(219,248)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	498,140	498,234
Payments on unsecured debt and mortgage notes	(102,563)	(360,975)
Proceeds from lines of credit	1,038,426	567,029
Repayments of lines of credit	(743,426)	(567,029)
Retirement of common stock	(176,311)	(56,989)
Additions to deferred charges	(5,172)	(5,445)
Net proceeds from issuance of common stock	(70)	(20)
Net proceeds from stock options exercised	14,329	6,699
Payments related to tax withholding for share-based compensation	(5,664)	(3,495)
Distributions to noncontrolling interest	(7,478)	(6,978)
Redemption of noncontrolling interest	(1,368)	(12,213)
Redemption of redeemable noncontrolling interest	0	(73)
Common stock dividends paid	(128,879)	(122,525)
Net cash provided by (used in) financing activities	379,964	(63,780)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	201,253	(27,269)
Unrestricted and restricted cash and cash equivalents at beginning of period	81,094	151,395	$ 151,395
Unrestricted and restricted cash and cash equivalents at end of period	282,347	124,126	81,094
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $4.8 million and $5.9 million capitalized in 2020 and 2019, respectively)	52,487	41,914
Operating cash flows from operating leases	1,715	1,694
Supplemental disclosure of noncash investing and financing activities:
Transfers between real estate under development and rental properties, net	131,841	0
Transfer from real estate under development to co-investments	824	313
Reclassifications (from) to redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest	(4,767)	1,767
Initial recognition of operating lease right-of-use assets	0	77,645
Initial recognition of operating lease liabilities	0	79,693
Essex Portfolio, L.P.
Cash flows from operating activities:
Net income	328,765	125,505
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	131,559	120,568
Amortization of discount on marketable securities	(2,394)	(5,311)
Amortization of discount and debt financing costs, net	2,297	529
Loss on sale of marketable securities	13	58
Unrealized (gain) loss on equity securities recognized through income	8,696	(4,510)
Earnings from co-investments	(21,297)	(16,276)
Operating distributions from co-investments	19,388	17,804
Accrued interest from notes and other receivables	(355)	(1,424)
Equity-based compensation	1,405	2,068
Gain on early retirement of debt, net	(321)	(1,336)
Gain on remeasurement of co-investment	(234,694)	(31,535)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets	(172)	(4,730)
Accounts payable, accrued liabilities, and operating lease liabilities	32,808	53,895
Other liabilities	1,278	454
Net cash provided by operating activities	266,926	255,759
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired	(458,302)	(44,984)
Redevelopment	(18,296)	(14,157)
Development acquisitions of and additions to real estate under development	(25,681)	(39,306)
Capital expenditures on rental properties	(17,151)	(17,075)
Collections of notes and other receivables	98,711	2,500
Proceeds from insurance for property losses	457	1,583
Contributions to co-investments	(21,905)	(126,248)
Changes in refundable deposits	96	5
Purchases of marketable securities	(10,731)	(8,413)
Sales and maturities of marketable securities	165	16,847
Non-operating distributions from co-investments	7,000	10,000
Net cash used in investing activities	(445,637)	(219,248)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	498,140	498,234
Payments on unsecured debt and mortgage notes	(102,563)	(360,975)
Proceeds from lines of credit	1,038,426	567,029
Repayments of lines of credit	(743,426)	(567,029)
Retirement of common stock	(176,311)	(56,989)
Additions to deferred charges	(5,172)	(5,445)
Net proceeds from issuance of common stock	(70)	(20)
Net proceeds from stock options exercised	14,329	6,699
Payments related to tax withholding for share-based compensation	(5,664)	(3,495)
Distributions to noncontrolling interest	(2,016)	(1,959)
Redemption of noncontrolling interest	(1,368)	(12,213)
Redemption of redeemable noncontrolling interest	0	(73)
Common stock dividends paid	(134,341)	(127,544)
Net cash provided by (used in) financing activities	379,964	(63,780)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	201,253	(27,269)
Unrestricted and restricted cash and cash equivalents at beginning of period	81,094	151,395	151,395
Unrestricted and restricted cash and cash equivalents at end of period	282,347	124,126	$ 81,094
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $4.8 million and $5.9 million capitalized in 2020 and 2019, respectively)	52,487	41,914
Operating cash flows from operating leases	1,715	1,694
Supplemental disclosure of noncash investing and financing activities:
Transfers between real estate under development and rental properties, net	131,841	0
Transfer from real estate under development to co-investments	824	313
Reclassifications (from) to redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest	(4,767)	1,767
Initial recognition of operating lease right-of-use assets	0	77,645
Initial recognition of operating lease liabilities	$ 0	$ 79,693