Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 96,639	$ 187,551
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	119,105	115,503
Amortization of discount on marketable securities	(4,157)	(3,573)
Amortization of (premium) discount and debt financing costs, net	(664)	(3,309)
Gain on sale of marketable securities and other investments	(680)	(1,605)
Unrealized loss on equity securities recognized through income	876	0
Earnings from co-investments	(32,774)	(10,899)
Operating distributions from co-investments	40,437	12,358
Accrued interest from notes and other receivables	(1,294)	(647)
Gain on the sale of real estate and land	0	(26,174)
Equity-based compensation	2,090	1,253
Gain on remeasurement of co-investment	0	(86,482)
Changes in operating assets and liabilities:
Prepaid expenses, receivables and other assets	(3,716)	(3,889)
Accounts payable and accrued liabilities	52,151	42,482
Other liabilities	345	737
Net cash provided by operating activities	268,358	223,306
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures	(2,873)	(187,917)
Redevelopment	(15,893)	(12,240)
Development acquisitions of and additions to real estate under development	(38,203)	(30,457)
Capital expenditures on rental properties	(14,947)	(10,885)
Investments in notes receivable	0	(8,750)
Collections of notes receivable	29,500	0
Proceeds from insurance for property losses	565	435
Proceeds from dispositions of real estate	0	131,230
Contributions to co-investments	(56,020)	(120,816)
Changes in refundable deposits	410	512
Purchases of marketable securities	(13,437)	(20,939)
Sales and maturities of marketable securities	9,579	24,903
Non-operating distributions from co-investments	2,330	55,025
Net cash used in investing activities	(98,989)	(179,899)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	298,773	250,000
Payments on unsecured debt and mortgage notes	(83,748)	(308,020)
Proceeds from lines of credit	256,832	404,562
Repayments of lines of credit	(435,832)	(353,329)
Retirement of common stock	(3,774)	0
Additions to deferred charges	(3,283)	(1,014)
Net proceeds from issuance of common stock	(67)	(65)
Net proceeds from stock options exercised	1,222	5,794
Payments related to tax withholding for share-based compensation	(11)	(33)
Distributions to noncontrolling interest	(5,926)	(5,425)
Redemption of noncontrolling interest	0	(1,070)
Common and preferred stock dividends paid	(115,603)	(104,857)
Net cash used in financing activities	(91,417)	(113,457)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	77,952	(70,050)
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	139,078	100,252
Supplemental disclosure of cash flow information:
Cash paid for interest, net of $4.2 million and $3.3 million capitalized in 2018 and 2017, respectively	40,306	48,397
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	1	747
Transfer from real estate under development to co-investments	365	2,080
Reclassifications to redeemable noncontrolling interest from additional paid in capital and noncontrolling interest	1,953	731
Debt assumed in connection with acquisition	0	51,882
Essex Portfolio, L.P. [Member]
Cash flows from operating activities:
Net income	96,639	187,551
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	119,105	115,503
Amortization of discount on marketable securities	(4,157)	(3,573)
Amortization of (premium) discount and debt financing costs, net	(664)	(3,309)
Gain on sale of marketable securities and other investments	(680)	(1,605)
Unrealized loss on equity securities recognized through income	876	0
Earnings from co-investments	(32,774)	(10,899)
Operating distributions from co-investments	40,437	12,358
Accrued interest from notes and other receivables	(1,294)	(647)
Gain on the sale of real estate and land	0	(26,174)
Equity-based compensation	2,090	1,253
Gain on remeasurement of co-investment	0	(86,482)
Changes in operating assets and liabilities:
Prepaid expenses, receivables and other assets	(3,716)	(3,889)
Accounts payable and accrued liabilities	52,151	42,482
Other liabilities	345	737
Net cash provided by operating activities	268,358	223,306
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures	(2,873)	(187,917)
Redevelopment	(15,893)	(12,240)
Development acquisitions of and additions to real estate under development	(38,203)	(30,457)
Capital expenditures on rental properties	(14,947)	(10,885)
Investments in notes receivable	0	(8,750)
Collections of notes receivable	29,500	0
Proceeds from insurance for property losses	565	435
Proceeds from dispositions of real estate	0	131,230
Contributions to co-investments	(56,020)	(120,816)
Changes in refundable deposits	410	512
Purchases of marketable securities	(13,437)	(20,939)
Sales and maturities of marketable securities	9,579	24,903
Non-operating distributions from co-investments	2,330	55,025
Net cash used in investing activities	(98,989)	(179,899)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	298,773	250,000
Payments on unsecured debt and mortgage notes	(83,748)	(308,020)
Proceeds from lines of credit	256,832	404,562
Repayments of lines of credit	(435,832)	(353,329)
Retirement of common stock	(3,774)	0
Additions to deferred charges	(3,283)	(1,014)
Net proceeds from issuance of common stock	(67)	(65)
Net proceeds from stock options exercised	1,222	5,794
Payments related to tax withholding for share-based compensation	(11)	(33)
Distributions to noncontrolling interest	(2,267)	(5,425)
Redemption of noncontrolling interest	0	(1,070)
Common and preferred stock dividends paid	(119,262)	(104,857)
Net cash used in financing activities	(91,417)	(113,457)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	77,952	(70,050)
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	139,078	100,252
Supplemental disclosure of cash flow information:
Cash paid for interest, net of $4.2 million and $3.3 million capitalized in 2018 and 2017, respectively	40,306	48,397
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	1	747
Transfer from real estate under development to co-investments	365	2,080
Reclassifications to redeemable noncontrolling interest from additional paid in capital and noncontrolling interest	1,953	731
Debt assumed in connection with acquisition	$ 0	$ 51,882