CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Operating Activities
Net income/(loss)	$ 221,542	$ 132,655	$ 320,380
Adjustments to reconcile net income/(loss) to net cash provided by/(used in) operating activities:
Depreciation and amortization	435,679	436,462	425,638
(Gain)/loss on sale of real estate owned	(136,197)	(43,404)	(226,199)
(Income)/loss from unconsolidated entities	5,055	(31,257)	(52,234)
Return on investment in unconsolidated joint ventures	4,248	4,416	57,578
Amortization of share-based compensation	14,244	12,862	13,398
Other	4,998	20,467	39,490
Changes in operating assets and liabilities:
(Increase)/decrease in operating assets	(13,880)	(9,008)	(29,399)
Increase/(decrease) in operating liabilities	24,987	(4,278)	(12,084)
Net cash provided by/(used in) operating activities	560,676	518,915	536,568
Investing Activities
Acquisition of real estate assets		(96,791)	(163,015)
Proceeds from sales of real estate investments, net	247,031	71,235	301,799
Development of real estate assets	(150,238)	(248,546)	(178,279)
Capital expenditures and other major improvements — real estate assets, net of escrow reimbursement	(112,359)	(124,728)	(91,740)
Capital expenditures — non-real estate assets	(4,850)	(1,384)	(4,439)
Investment in unconsolidated joint ventures	(112,025)	(123,842)	(40,162)
Distributions received from unconsolidated joint ventures	42,683	116,329	66,116
Purchase deposits on pending acquisitions	(1,000)
Repayment/(issuance) of notes receivable, net	(22,790)	321	(3,000)
Net cash provided by/(used in) investing activities	(113,548)	(407,406)	(112,720)
Financing Activities
Payments on secured debt	(279,243)	(326,346)	(375,308)
Proceeds from the issuance of secured debt	80,000		50,000
Payments on unsecured debt		(300,000)	(95,053)
Net proceeds from the issuance of unsecured debt	299,994	598,095	300,000
Net proceeds/(repayment) of commercial paper	(198,885)	300,000
Net proceeds/(repayment) of revolving bank debt	(21,751)	417	(128,650)
Proceeds from the issuance of common shares through public offering, net	299,825		173,211
Repurchase of common shares	(19,988)
Distributions paid to redeemable noncontrolling interests	(32,457)	(31,089)	(29,688)
Distributions paid to preferred stockholders	(3,836)	(3,708)	(3,717)
Distributions paid to common stockholders	(342,241)	(327,793)	(308,923)
Other	(41,485)	(21,361)	(11,154)
Net cash provided by/(used in) financing activities	(260,067)	(111,785)	(429,282)
Net increase/(decrease) in cash, cash equivalents, and restricted cash	187,061	(276)	(5,434)
Cash, cash equivalents, and restricted cash, beginning of year	21,830	22,106	27,540
Cash, cash equivalents, and restricted cash, end of year	208,891	21,830	22,106
Supplemental Information:
Interest paid during the period, net of amounts capitalized	132,466	126,348	124,635
Cash paid/(refunds received) for income taxes	625	1,660	693
Non-cash transactions:
Transfer of investment in and advances to unconsolidated joint ventures to real estate owned		140,549	80,583
Secured debt assumed in the consolidation of unconsolidated joint ventures			75,796
Fair value adjustment of secured debt assumed in the consolidation of unconsolidated joint ventures			4,228
Vesting of LTIP Units	4,397	2,317
Development costs and capital expenditures incurred but not yet paid	10,304	43,930	46,285
Conversion of Operating Partnership and DownREIT Partnership noncontrolling interests to common stock (348,057 shares in 2018; 389,033 shares in 2017; and 260,292 shares in 2016)	13,328	14,544	9,466
Distributions declared but not yet paid	$ 97,666	$ 91,455	$ 86,936