Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ 19,574	$ 52,690	$ (5,209)	$ 144,183
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization			174,353	190,783
Amortization of deferred loan costs and debt premiums			5,237	5,911
(Accretion) and amortization of above and below market lease intangibles, net			(22,456)	(19,496)
Stock-based compensation, net of capitalization			7,217	6,989
Equity in income of investments in real estate partnerships	(2,824)	(13,128)	(14,242)	(43,955)
Gain on sale of real estate, net of tax			(45,453)	(16,932)
Provision for impairment of real estate, net of tax	230	10,441	1,014	12,113
Goodwill impairment	0		132,128	0
Early extinguishment of debt			0	10,591
Distribution of earnings from investments in real estate partnerships			18,655	25,659
Settlement of derivative instruments			0	(5,719)
Deferred compensation expense			(441)	3,297
Realized and unrealized gain on investments			599	(3,299)
Changes in assets and liabilities:
Tenant and other receivables			(24,111)	6,975
Deferred leasing costs			(3,732)	(4,782)
Other assets			(8,499)	(7,628)
Accounts payable and other liabilities			10,982	(3,292)
Tenants’ security, escrow deposits and prepaid rent			(8,623)	(12,075)
Net cash provided by operating activities			217,419	289,323
Cash flows from investing activities:
Acquisition of operating real estate			(16,867)	(19,302)
Advance deposits refunded (paid) on acquisition of operating real estate			100	(11,000)
Real estate development and capital improvements			(107,852)	(80,032)
Proceeds from sale of real estate investments			115,614	83,460
Issuance of notes receivable			(440)	0
Investments in real estate partnerships			(42,088)	(32,970)
Return of capital from investments in real estate partnerships			23,235	46,740
Dividends on investment securities			140	264
Acquisition of investment securities			(7,062)	(11,498)
Proceeds from sale of investment securities			7,094	10,828
Net cash used in investing activities			(28,126)	(13,510)
Cash flows from financing activities:
Net proceeds from common stock issuance			125,616	0
Repurchase of common shares in conjunction with equity award plans			(5,405)	(6,148)
Common shares repurchased through share repurchase program			0	(32,778)
Proceeds from sale of treasury stock			62	9
Distributions to limited partners in consolidated partnerships, net			(1,644)	(968)
Distributions to exchangeable operating partnership unit holders			(910)	(409)
Dividends paid to common stockholders			(199,971)	(195,246)
Repayment of fixed rate unsecured notes			0	(250,000)
Proceeds from issuance of fixed rate unsecured notes, net			598,830	298,983
Proceeds from unsecured credit facilities			610,000	185,000
Repayment of unsecured credit facilities			(830,000)	(210,000)
Repayment of notes payable			(3,891)	(53,530)
Scheduled principal payments			(5,128)	(4,562)
Payment of loan costs			(5,056)	(3,343)
Early redemption costs			0	(10,647)
Net cash provided by (used in) financing activities			282,503	(283,639)
Net increase (decrease) in cash and cash equivalents and restricted cash			471,796	(7,826)
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	587,358	37,364	587,358	37,364	115,562
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $2,449 and $1,996 in 2020 and 2019, respectively)			72,013	68,351
Cash paid for income taxes, net of refunds			576	459
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
Exchangeable operating partnership units issued for acquisition of real estate			1,275
Change in accrued capital expenditures			2,965	9,149
Common stock issued under dividend reinvestment plan	377	357	756	740
Stock-based compensation capitalized			604	1,105
Contributions from limited partners in consolidated partnerships, net				66
Common stock issued for dividend reinvestment in trust			540	479
Contribution of stock awards into trust			1,352	2,397
Distribution of stock held in trust			441	167
Change in fair value of securities			326	260
Partnership Interest [Member]
Cash flows from operating activities:
Net income (loss)	19,574	52,690	(5,209)	144,183
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization			174,353	190,783
Amortization of deferred loan costs and debt premiums			5,237	5,911
(Accretion) and amortization of above and below market lease intangibles, net			(22,456)	(19,496)
Stock-based compensation, net of capitalization			7,217	6,989
Equity in income of investments in real estate partnerships	(2,824)	(13,128)	(14,242)	(43,955)
Gain on sale of real estate, net of tax			(45,453)	(16,932)
Provision for impairment of real estate, net of tax	230	10,441	1,014	12,113
Goodwill impairment			132,128	0
Early extinguishment of debt			0	10,591
Distribution of earnings from investments in real estate partnerships			18,655	25,659
Settlement of derivative instruments			0	(5,719)
Deferred compensation expense			(441)	3,297
Realized and unrealized gain on investments			599	(3,299)
Changes in assets and liabilities:
Tenant and other receivables			(24,111)	6,975
Deferred leasing costs			(3,732)	(4,782)
Other assets			(8,499)	(7,628)
Accounts payable and other liabilities			10,982	(3,292)
Tenants’ security, escrow deposits and prepaid rent			(8,623)	(12,075)
Net cash provided by operating activities			217,419	289,323
Cash flows from investing activities:
Acquisition of operating real estate			(16,867)	(19,302)
Advance deposits refunded (paid) on acquisition of operating real estate			100	(11,000)
Real estate development and capital improvements			(107,852)	(80,032)
Proceeds from sale of real estate investments			115,614	83,460
Issuance of notes receivable			(440)	0
Investments in real estate partnerships			(42,088)	(32,970)
Return of capital from investments in real estate partnerships			23,235	46,740
Dividends on investment securities			140	264
Acquisition of investment securities			(7,062)	(11,498)
Proceeds from sale of investment securities			7,094	10,828
Net cash used in investing activities			(28,126)	(13,510)
Cash flows from financing activities:
Net proceeds from common stock issuance			125,616	0
Repurchase of common shares in conjunction with equity award plans			(5,405)	(6,148)
Common shares repurchased through share repurchase program			0	(32,778)
Proceeds from sale of treasury stock			62	9
Distributions to limited partners in consolidated partnerships, net			(1,644)	(968)
Dividends paid to common stockholders			(200,881)	(195,655)
Repayment of fixed rate unsecured notes			0	(250,000)
Proceeds from issuance of fixed rate unsecured notes, net			598,830	298,983
Proceeds from unsecured credit facilities			610,000	185,000
Repayment of unsecured credit facilities			(830,000)	(210,000)
Repayment of notes payable			(3,891)	(53,530)
Scheduled principal payments			(5,128)	(4,562)
Payment of loan costs			(5,056)	(3,343)
Early redemption costs			0	(10,647)
Net cash provided by (used in) financing activities			282,503	(283,639)
Net increase (decrease) in cash and cash equivalents and restricted cash			471,796	(7,826)
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	$ 587,358	$ 37,364	587,358	37,364	$ 115,562
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $2,449 and $1,996 in 2020 and 2019, respectively)			72,013	68,351
Cash paid for income taxes, net of refunds			576	459
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
Exchangeable operating partnership units issued for acquisition of real estate			1,275
Change in accrued capital expenditures			2,965	9,149
Common stock issued under dividend reinvestment plan			756	740
Stock-based compensation capitalized			604	1,105
Contributions from limited partners in consolidated partnerships, net				66
Common stock issued for dividend reinvestment in trust			540	479
Contribution of stock awards into trust			1,352	2,397
Distribution of stock held in trust			441	167
Change in fair value of securities			$ 326	$ 260