Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 13,310	$ 57,944	$ 8,101	$ 202,127
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			259,161	282,639
Amortization of deferred loan costs and debt premiums			7,566	8,533
(Accretion) and amortization of above and below market lease intangibles, net			(29,847)	(30,196)
Stock-based compensation, net of capitalization			10,654	10,716
Equity in income of investments in real estate partnerships	(8,116)	283	(22,358)	(43,673)
Gain on sale of real estate, net of tax			(48,690)	(17,819)
Provision for impairment of real estate, net of tax		(14)	1,014	12,099
Goodwill impairment			132,128
Early extinguishment of debt	19,358	1,391	19,358	11,982
Distribution of earnings from investments in real estate partnerships			32,659	41,427
Settlement of derivative instruments				(6,870)
Deferred compensation expense			1,381	3,551
Realized and unrealized gain on investments			(1,427)	(3,634)
Changes in assets and liabilities:
Tenant and other receivables			4,072	520
Deferred leasing costs			(4,999)	(4,695)
Other assets			(7,670)	(7,182)
Accounts payable and other liabilities			20,223	14,886
Tenants’ security, escrow deposits and prepaid rent			(6,737)	(5,055)
Net cash provided by operating activities			374,589	469,356
Cash flows from investing activities:
Acquisition of operating real estate			(16,867)	(222,230)
Advance deposits refunded (paid) on acquisition of operating real estate			100	(600)
Real estate development and capital improvements			(149,293)	(128,085)
Proceeds from sale of real estate investments			125,539	98,006
Issuance of notes receivable			(551)
Investments in real estate partnerships			(47,957)	(57,333)
Return of capital from investments in real estate partnerships			23,235	46,740
Dividends on investment securities			193	400
Acquisition of investment securities			(10,580)	(17,955)
Proceeds from sale of investment securities			10,659	14,748
Net cash used in investing activities			(65,522)	(266,309)
Cash flows from financing activities:
Net proceeds from common stock issuance			125,608
Repurchase of common shares in conjunction with equity award plans			(5,512)	(6,165)
Common shares repurchased through share repurchase program				(32,777)
Proceeds from sale of treasury stock			269	9
Distributions to limited partners in consolidated partnerships, net			(2,193)	(2,223)
Distributions to exchangeable operating partnership unit holders			(1,366)	(614)
Dividends paid to common stockholders			(300,538)	(292,921)
Repayment of fixed rate unsecured notes			(300,000)	(250,000)
Proceeds from issuance of fixed rate unsecured notes, net			598,830	723,571
Proceeds from unsecured credit facilities			610,000	450,000
Repayment of unsecured credit facilities			(830,000)	(710,000)
Repayment of notes payable			(3,891)	(55,030)
Scheduled principal payments			(8,149)	(6,960)
Payment of loan costs			(5,063)	(7,019)
Early redemption costs			(21,748)	(10,647)
Net cash used in financing activities			(143,753)	(200,776)
Net increase in cash and cash equivalents and restricted cash			165,314	2,271
Cash and cash equivalents and restricted cash at beginning of the period			115,562	45,190	$ 45,190
Cash and cash equivalents and restricted cash at end of the period	280,876	47,461	280,876	47,461	115,562
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $3,590 and $3,089 in 2020 and 2019, respectively)			121,307	112,055
Cash paid for income taxes, net of refunds			898	778
Supplemental disclosure of non-cash transactions:
Acquisition of real estate previously held within investments in real estate partnerships			5,986
Mortgage loan assumed with the acquisition of real estate			16,359	26,152
Mortgage loan assumed by purchaser with the sale of real estate			8,250
Exchangeable operating partnership units issued for acquisition of real estate		25,869	1,275	25,869
Change in accrued capital expenditures			16,276	3,185
Common stock issued under dividend reinvestment plan	382	345	1,138	1,085
Stock-based compensation capitalized			650	1,719
(Distributions to) contributions from limited partners in consolidated partnerships, net			(1,420)	66
Common stock issued for dividend reinvestment in trust			819	732
Contribution of stock awards into trust			1,439	2,496
Distribution of stock held in trust			442	197
Change in fair value of securities			288	509
Partnership Interest [Member]
Cash flows from operating activities:
Net income	13,310	57,944	8,101	202,127
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			259,161	282,639
Amortization of deferred loan costs and debt premiums			7,566	8,533
(Accretion) and amortization of above and below market lease intangibles, net			(29,847)	(30,196)
Stock-based compensation, net of capitalization			10,654	10,716
Equity in income of investments in real estate partnerships	(8,116)	283	(22,358)	(43,673)
Gain on sale of real estate, net of tax			(48,690)	(17,819)
Provision for impairment of real estate, net of tax		(14)	1,014	12,099
Goodwill impairment			132,128
Early extinguishment of debt	19,358	1,391	19,358	11,982
Distribution of earnings from investments in real estate partnerships			32,659	41,427
Settlement of derivative instruments				(6,870)
Deferred compensation expense			1,381	3,551
Realized and unrealized gain on investments			(1,427)	(3,634)
Changes in assets and liabilities:
Tenant and other receivables			4,072	520
Deferred leasing costs			(4,999)	(4,695)
Other assets			(7,670)	(7,182)
Accounts payable and other liabilities			20,223	14,886
Tenants’ security, escrow deposits and prepaid rent			(6,737)	(5,055)
Net cash provided by operating activities			374,589	469,356
Cash flows from investing activities:
Acquisition of operating real estate			(16,867)	(222,230)
Advance deposits refunded (paid) on acquisition of operating real estate			100	(600)
Real estate development and capital improvements			(149,293)	(128,085)
Proceeds from sale of real estate investments			125,539	98,006
Issuance of notes receivable			(551)
Investments in real estate partnerships			(47,957)	(57,333)
Return of capital from investments in real estate partnerships			23,235	46,740
Dividends on investment securities			193	400
Acquisition of investment securities			(10,580)	(17,955)
Proceeds from sale of investment securities			10,659	14,748
Net cash used in investing activities			(65,522)	(266,309)
Cash flows from financing activities:
Net proceeds from common stock issuance			125,608
Repurchase of common shares in conjunction with equity award plans			(5,512)	(6,165)
Common shares repurchased through share repurchase program				(32,777)
Proceeds from sale of treasury stock			269	9
Distributions to limited partners in consolidated partnerships, net			(2,193)	(2,223)
Dividends paid to common stockholders			(301,904)	(293,535)
Repayment of fixed rate unsecured notes			(300,000)	(250,000)
Proceeds from issuance of fixed rate unsecured notes, net			598,830	723,571
Proceeds from unsecured credit facilities			610,000	450,000
Repayment of unsecured credit facilities			(830,000)	(710,000)
Repayment of notes payable			(3,891)	(55,030)
Scheduled principal payments			(8,149)	(6,960)
Payment of loan costs			(5,063)	(7,019)
Early redemption costs			(21,748)	(10,647)
Net cash used in financing activities			(143,753)	(200,776)
Net increase in cash and cash equivalents and restricted cash			165,314	2,271
Cash and cash equivalents and restricted cash at beginning of the period			115,562	45,190	45,190
Cash and cash equivalents and restricted cash at end of the period	$ 280,876	47,461	280,876	47,461	$ 115,562
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $3,590 and $3,089 in 2020 and 2019, respectively)			121,307	112,055
Cash paid for income taxes, net of refunds			898	778
Supplemental disclosure of non-cash transactions:
Acquisition of real estate previously held within investments in real estate partnerships			5,986
Mortgage loan assumed with the acquisition of real estate			16,359	26,152
Mortgage loan assumed by purchaser with the sale of real estate			8,250
Exchangeable operating partnership units issued for acquisition of real estate		$ 25,869	1,275	25,869
Change in accrued capital expenditures			16,276	3,185
Common stock issued under dividend reinvestment plan			1,138	1,085
Stock-based compensation capitalized			650	1,719
(Distributions to) contributions from limited partners in consolidated partnerships, net			(1,420)	66
Common stock issued for dividend reinvestment in trust			819	732
Contribution of stock awards into trust			1,439	2,496
Distribution of stock held in trust			442	197
Change in fair value of securities			$ 288	$ 509