Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 47,317	$ 243,258	$ 252,325
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	345,900	374,283	359,688
Amortization of deferred loan costs and debt premiums	9,023	11,170	10,476
(Accretion) and amortization of above and below market lease intangibles, net	(40,540)	(43,867)	(33,330)
Stock-based compensation, net of capitalization	13,581	14,339	13,635
Equity in income of investments in real estate partnerships	(34,169)	(60,956)	(42,974)
Gain on sale of real estate, net of tax	(67,465)	(24,242)	(28,343)
Provision for impairment of real estate, net of tax	18,536	54,174	38,437
Goodwill impairment	132,128	0	0
Early extinguishment of debt	21,837	11,982	11,172
Distribution of earnings from investments in real estate partnerships	47,703	56,297	54,266
Settlement of derivative instrument	0	(6,870)	0
Deferred compensation expense	4,668	5,169	(1,085)
Realized and unrealized gain on investments	(5,519)	(5,433)	1,177
Changes in assets and liabilities:
Tenant and other receivables	16,944	(4,690)	(26,374)
Deferred leasing costs	(6,973)	(6,777)	(8,366)
Other assets	(1,200)	(1,570)	(1,410)
Accounts payable and other liabilities	997	4,175	(760)
Tenants’ security, escrow deposits and prepaid rent	(3,650)	829	11,793
Net cash provided by operating activities	499,118	621,271	610,327
Cash flows from investing activities:
Acquisition of operating real estate	(16,867)	(222,444)	(85,289)
Advance deposits refunded (paid) on acquisition of operating real estate	100	(125)	0
Real estate development and capital improvements	(180,804)	(200,012)	(226,191)
Proceeds from sale of real estate investments	189,444	137,572	250,445
Proceeds from property insurance casualty claims	7,957	9,350	0
(Issuance) collection of notes receivable	(1,340)	(547)	15,648
Investments in real estate partnerships	(51,440)	(66,921)	(74,238)
Return of capital from investments in real estate partnerships	32,125	63,693	14,647
Dividends on investment securities	353	660	531
Acquisition of investment securities	(25,155)	(23,458)	(23,164)
Proceeds from sale of investment securities	19,986	19,539	21,587
Net cash used in investing activities	(25,641)	(282,693)	(106,024)
Cash flows from financing activities:
Net proceeds from common stock issuance	125,608	0	0
Repurchase of common shares/units in conjunction with tax withholdings on equity award plans	(5,512)	(6,204)	(6,772)
Proceeds from sale of treasury stock	269	9	99
Common shares repurchased through share repurchase program	0	(32,778)	(213,851)
Distributions to limited partners in consolidated partnerships, net	(2,770)	(3,367)	(4,526)
Distributions to exchangeable operating partnership unit holders	(1,366)	(1,051)	(777)
Dividends paid to common stockholders/ Distributions to partners	(300,537)	(390,598)	(375,978)
Repayment of fixed rate unsecured notes	(300,000)	(250,000)	(150,000)
Proceeds from issuance of fixed rate unsecured notes, net	598,830	723,571	299,511
Proceeds from unsecured credit facilities	610,000	560,000	575,000
Repayment of unsecured credit facilities	(830,000)	(785,000)	(490,000)
Proceeds from notes payable	0	0	1,740
Repayment of notes payable	(67,189)	(55,680)	(113,037)
Scheduled principal payments	(11,104)	(9,442)	(9,964)
Payment of loan costs	(5,063)	(7,019)	(9,448)
Early redemption costs	(21,755)	(10,647)	(10,491)
Net cash used in financing activities	(210,589)	(268,206)	(508,494)
Net increase (decrease) in cash, cash equivalents, and restricted cash	262,888	70,372	(4,191)
Cash, cash equivalents, and restricted cash at beginning of the year	115,562	45,190	49,381
Cash, cash equivalents, and restricted cash at end of the year	378,450	115,562	45,190
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $4,355, $4,192, and $7,020 in 2020, 2019, and 2018, respectively)	151,338	136,139	136,645
Cash paid for income taxes, net of refunds	1,870	1,225	5,455
Supplemental disclosure of non-cash transactions:
Exchangeable operating partnership units issued for acquisition of real estate	1,275	25,870
Acquisition of real estate previously held within investments in real estate partnerships	5,986
Mortgage loans for the acquisition of real estate	16,359	26,152	9,700
Mortgage loan assumed by purchaser with the sale of real estate	8,250
Change in fair value of securities	315	660	(206)
Change in accrued capital expenditures	12,166	10,704
Common stock issued for dividend reinvestment plan	1,139	1,429	1,333
Stock-based compensation capitalized	1,119	2,325	3,509
Common stock and exchangeable operating partnership dividends declared but not yet paid	101,412
Common stock issued for dividend reinvestment in trust	819	987	841
Contribution of stock awards into trust	1,524	2,582	1,314
Distribution of stock held in trust	1,052	197	524
Common stock issued under dividend reinvestment plan	1,139	1,429	1,333
(Distributions to) Contributions from limited partners in consolidated partnerships, net	(1,512)	66	13,000
Partnership Interest [Member]
Cash flows from operating activities:
Net income	47,317	243,258	252,325
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	345,900	374,283	359,688
Amortization of deferred loan costs and debt premiums	9,023	11,170	10,476
(Accretion) and amortization of above and below market lease intangibles, net	(40,540)	(43,867)	(33,330)
Stock-based compensation, net of capitalization	13,581	14,339	13,635
Equity in income of investments in real estate partnerships	(34,169)	(60,956)	(42,974)
Gain on sale of real estate, net of tax	(67,465)	(24,242)	(28,343)
Provision for impairment of real estate, net of tax	18,536	54,174	38,437
Goodwill impairment	132,128	0	0
Early extinguishment of debt	21,837	11,982	11,172
Distribution of earnings from investments in real estate partnerships	47,703	56,297	54,266
Settlement of derivative instrument	0	(6,870)	0
Deferred compensation expense	4,668	5,169	(1,085)
Realized and unrealized gain on investments	(5,519)	(5,433)	1,177
Changes in assets and liabilities:
Tenant and other receivables	16,944	(4,690)	(26,374)
Deferred leasing costs	(6,973)	(6,777)	(8,366)
Other assets	(1,200)	(1,570)	(1,410)
Accounts payable and other liabilities	997	4,175	(760)
Tenants’ security, escrow deposits and prepaid rent	(3,650)	829	11,793
Net cash provided by operating activities	499,118	621,271	610,327
Cash flows from investing activities:
Acquisition of operating real estate	(16,867)	(222,444)	(85,289)
Advance deposits refunded (paid) on acquisition of operating real estate	100	(125)	0
Real estate development and capital improvements	(180,804)	(200,012)	(226,191)
Proceeds from sale of real estate investments	189,444	137,572	250,445
Proceeds from property insurance casualty claims	7,957	9,350	0
(Issuance) collection of notes receivable	(1,340)	(547)	15,648
Investments in real estate partnerships	(51,440)	(66,921)	(74,238)
Return of capital from investments in real estate partnerships	32,125	63,693	14,647
Dividends on investment securities	353	660	531
Acquisition of investment securities	(25,155)	(23,458)	(23,164)
Proceeds from sale of investment securities	19,986	19,539	21,587
Net cash used in investing activities	(25,641)	(282,693)	(106,024)
Cash flows from financing activities:
Net proceeds from common stock issuance	125,608
Repurchase of common shares/units in conjunction with tax withholdings on equity award plans	(5,512)	(6,204)	(6,772)
Proceeds from sale of treasury stock	269	9	99
Common shares repurchased through share repurchase program	0	(32,778)	(213,851)
Distributions to limited partners in consolidated partnerships, net	(2,770)	(3,367)	(4,526)
Dividends paid to common stockholders/ Distributions to partners	(301,903)	(391,649)	(376,755)
Repayment of fixed rate unsecured notes	(300,000)	(250,000)	(150,000)
Proceeds from issuance of fixed rate unsecured notes, net	598,830	723,571	299,511
Proceeds from unsecured credit facilities	610,000	560,000	575,000
Repayment of unsecured credit facilities	(830,000)	(785,000)	(490,000)
Proceeds from notes payable	0	0	1,740
Repayment of notes payable	(67,189)	(55,680)	(113,037)
Scheduled principal payments	(11,104)	(9,442)	(9,964)
Payment of loan costs	(5,063)	(7,019)	(9,448)
Early redemption costs	(21,755)	(10,647)	(10,491)
Net cash used in financing activities	(210,589)	(268,206)	(508,494)
Net increase (decrease) in cash, cash equivalents, and restricted cash	262,888	70,372	(4,191)
Cash, cash equivalents, and restricted cash at beginning of the year	115,562	45,190	49,381
Cash, cash equivalents, and restricted cash at end of the year	378,450	115,562	45,190
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $4,355, $4,192, and $7,020 in 2020, 2019, and 2018, respectively)	151,338	136,139	136,645
Cash paid for income taxes, net of refunds	1,870	1,225	5,455
Supplemental disclosure of non-cash transactions:
Exchangeable operating partnership units issued for acquisition of real estate	1,275	25,870
Mortgage loans for the acquisition of real estate	16,359	26,152	9,700
Change in fair value of securities	315	660	(206)
Change in accrued capital expenditures	12,166	10,704
Common stock issued for dividend reinvestment plan	1,139	1,429	1,333
Stock-based compensation capitalized	1,119	2,325	3,509
Common stock and exchangeable operating partnership dividends declared but not yet paid	101,412
Common stock issued for dividend reinvestment in trust	819	987	841
Contribution of stock awards into trust	1,524	2,582	1,314
Distribution of stock held in trust	1,052	197	524
Common stock issued by Parent Company for partnership units exchanged	1,275	25,870
Acquisition of real estate previously held within investments in real estate partnerships	5,986
Mortgage loan assumed by purchaser with the sale of real estate	8,250
Common stock issued under dividend reinvestment plan	1,139	1,429	1,333
(Distributions to) Contributions from limited partners in consolidated partnerships, net	$ (1,512)	$ 66	$ 13,000