CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 876,660	$ 1,033,708	$ 741,733
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation expense	584,150	531,434	477,923
Amortization of deferred financing costs	7,657	7,661	6,871
Amortization of debt premium	(5,915)	(18,866)	(24,261)
Loss (gain) on extinguishment of debt, net	25,472	7,075	(26,736)
Amortization of stock-based compensation	17,920	15,082	15,321
Equity in (income) loss of, and return on, unconsolidated real estate entities and noncontrolling interests, net of eliminations	(19,798)	8,870	12,225
Casualty and impairment loss (gain), net	8,568	(3,935)	(17,303)
Abandonment of development pursuits	388	1,743	0
Cash flow hedge losses reclassified to earnings	7,070	6,433	5,774
Gain on sale of real estate assets	(281,745)	(442,916)	(158,852)
Decrease (increase) in resident security deposits, prepaid expenses and other assets	3,076	(5,403)	12,783
Increase in accrued expenses, other liabilities and accrued interest payable	32,754	19,386	29,189
Net cash provided by operating activities	1,256,257	1,160,272	1,074,667
Cash flows from investing activities:
Development/redevelopment of real estate assets including land acquisitions and deferred development costs	(979,947)	(1,201,026)	(1,569,326)
Acquisition of real estate assets, including partnership interest	(462,317)	(393,316)	0
Capital expenditures - existing real estate assets	(65,181)	(66,971)	(48,170)
Capital expenditures - non-real estate assets	(8,809)	(5,881)	(7,695)
Proceeds from sale of real estate, net of selling costs	503,039	532,717	282,163
Insurance proceeds for property damage claims	16,233	17,196	44,142
Mortgage note receivable lending	(17,590)	(19,115)	0
(Decrease) increase in payables for construction	(15,621)	2,196	(3,230)
Distributions from unconsolidated real estate entities	89,305	111,598	109,181
Investments in unconsolidated real estate entities	(24,493)	(9,750)	(6,582)
Net cash used in investing activities	(965,381)	(1,032,352)	(1,199,517)
Cash flows from financing activities:
Issuance of common stock, net	111,093	15,526	690,184
Dividends paid	(772,657)	(726,749)	(655,248)
Issuance of mortgage notes payable	206,800	0	0
Repayments of mortgage notes payable, including prepayment penalties	(1,313,025)	(168,076)	(853,604)
Issuance of unsecured notes	1,696,826	1,122,488	873,088
Repayment of unsecured notes, including prepayment penalties	(300,000)	(504,403)	0
Payment of deferred financing costs	(17,552)	(16,240)	(7,343)
Redemption of noncontrolling interest and units for cash by minority partners	0	0	(1,088)
Payment of capital lease obligation	(18,951)	0	0
Receipts (payments) for termination of forward interest rate swaps	391	(14,847)	0
Payments related to tax withholding for share-based compensation	(10,450)	(8,562)	(6,076)
Distributions to DownREIT partnership unitholders	(42)	(41)	(38)
Contributions from joint venture and profit-sharing partners	1,038	0	0
Distributions to joint venture and profit-sharing partners	(418)	(407)	(372)
Preferred interest obligation redemption and dividends	(2,000)	(1,960)	(14,410)
Net cash (used in) provided by financing activities	(418,947)	(303,271)	25,093
Net decrease in cash and cash equivalents	(128,071)	(175,351)	(99,757)
Cash and cash equivalents and restricted cash, beginning of year	329,977	505,328	605,085
Cash and cash equivalents and restricted cash, end of year	201,906	329,977	505,328
Cash paid during the year for interest, net of amount capitalized	207,842	194,059	188,782
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents and restricted cash, end of year	$ 329,977	$ 505,328	$ 605,085