CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 974,175	$ 876,660	$ 1,033,708
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	631,196	584,150	531,434
Amortization of deferred financing costs	7,939	7,657	7,661
Amortization of debt discount (premium)	1,701	(5,915)	(18,866)
Loss on extinguishment of debt, net	17,492	25,472	7,075
Amortization of stock-based compensation	20,280	17,920	15,082
Equity in loss (income) of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations	6,583	(19,798)	8,870
Casualty and impairment loss (gain), net	826	8,568	(3,935)
Abandonment of development pursuits	501	388	1,743
Cash flow hedge losses reclassified to earnings	6,143	7,070	6,433
Gain on sale of real estate assets	(385,976)	(281,745)	(442,916)
Decrease (increase) in resident security deposits, prepaid expenses and other assets	17,428	3,076	(5,403)
Increase in accrued expenses, other liabilities and accrued interest payable	2,823	32,754	19,386
Net cash provided by operating activities	1,301,111	1,256,257	1,160,272
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(1,139,954)	(979,947)	(1,201,026)
Acquisition of real estate assets, including partnership interest	(338,620)	(462,317)	(393,316)
Capital expenditures - existing real estate assets	(83,607)	(65,181)	(66,971)
Capital expenditures - non-real estate assets	(3,325)	(8,809)	(5,881)
Increase (decrease) in payables for construction	11,606	(15,621)	2,196
Proceeds from sale of real estate, net of selling costs	883,313	503,039	532,717
Insurance proceeds for property damage claims	0	16,233	17,196
Mortgage note receivable lending	(3,699)	(17,590)	(19,115)
Mortgage note receivable payments	53,136	0	0
Distributions from unconsolidated real estate entities	35,516	89,305	111,598
Investments in unconsolidated real estate entities	(11,017)	(24,493)	(9,750)
Net cash used in investing activities	(596,651)	(965,381)	(1,032,352)
Cash flows from financing activities:
Issuance of common stock, net	52,261	111,093	15,526
Dividends paid	(805,239)	(772,657)	(726,749)
Issuance of mortgage notes payable	295,939	206,800	0
Repayments of mortgage notes payable, including prepayment penalties	(255,452)	(1,313,025)	(168,076)
Issuance of unsecured notes	299,442	1,696,826	1,122,488
Repayment of unsecured notes, including prepayment penalties	(258,579)	(300,000)	(504,403)
Payment of deferred financing costs	(16,258)	(17,552)	(16,240)
Payment of capital lease obligation	(1,070)	(18,951)	0
Receipts (payments) for termination of forward interest rate swaps	12,598	391	(14,847)
Payments related to tax withholding for share-based compensation	(10,556)	(10,450)	(8,562)
Distributions to DownREIT partnership unitholders	(44)	(42)	(41)
Contributions from joint venture and profit-sharing partners	0	1,038	0
Distributions to joint venture and profit-sharing partners	(424)	(418)	(407)
Preferred interest obligation redemption and dividends	(1,120)	(2,000)	(1,960)
Net cash used in financing activities	(688,502)	(418,947)	(303,271)
Net increase (decrease) in cash and cash equivalents	15,958	(128,071)	(175,351)
Cash and cash equivalents and restricted cash, beginning of year	201,906	329,977	505,328
Cash and cash equivalents and restricted cash, end of year	217,864	201,906	329,977
Cash paid during the year for interest, net of amount capitalized	201,659	207,842	194,059
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents and restricted cash, end of year	$ 201,906	$ 329,977	$ 505,328