Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 52,690	$ 48,589	$ 144,183	$ 102,054
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			190,783	177,629
Amortization of deferred loan costs and debt premiums			5,911	4,999
(Accretion) and amortization of above and below market lease intangibles, net			(19,496)	(19,326)
Stock-based compensation, net of capitalization			6,989	6,574
Equity in income of investments in real estate partnerships	(13,128)	(9,174)	(43,955)	(19,523)
Gain on sale of real estate, net of tax			(16,932)	(1,219)
Provision for impairment, net of tax	10,441	12,533	12,113	28,587
Early extinguishment of debt		11,010	10,591	11,172
Distribution of earnings from operations of investments in real estate partnerships			25,659	26,711
Settlement of derivative instruments			(5,719)	0
Deferred compensation expense			3,297	544
Realized and unrealized gain on investments			(3,299)	(530)
Changes in assets and liabilities:
Tenant and other receivables			6,975	(3,802)
Deferred leasing costs			(4,782)	(3,404)
Other assets			(7,628)	(6,174)
Accounts payable and other liabilities			(3,292)	(6,052)
Tenants’ security, escrow deposits and prepaid rent			(12,075)	2,666
Net cash provided by operating activities			289,323	300,906
Cash flows from investing activities:
Acquisition of operating real estate			(19,302)	(85,766)
Advance deposits paid on acquisition of operating real estate			(11,000)	(2,025)
Real estate development and capital improvements			(80,032)	(120,579)
Proceeds from sale of real estate investments			83,460	42,508
Collection of notes receivable			0	15,648
Investments in real estate partnerships			(32,970)	(45,451)
Distributions received from investments in real estate partnerships			46,740	2,328
Dividends on investment securities			264	176
Acquisition of investment securities			(11,498)	(11,726)
Proceeds from sale of investment securities			10,828	10,976
Net cash used in investing activities			(13,510)	(193,911)
Cash flows from financing activities:
Repurchase of common shares in conjunction with equity award plans			(6,148)	(6,755)
Common shares repurchased through share repurchase program			(32,778)	(124,989)
Proceeds from sale of treasury stock			9	99
Distributions to limited partners in consolidated partnerships, net			(968)	(2,159)
Distributions to exchangeable operating partnership unit holders			(409)	(389)
Dividends paid to common stockholders			(195,246)	(188,559)
Repayment of fixed rate unsecured notes			(250,000)	(150,000)
Proceeds from issuance of fixed rate unsecured notes, net			298,983	299,511
Proceeds from unsecured credit facilities			185,000	400,000
Repayment of unsecured credit facilities			(210,000)	(310,000)
Proceeds from notes payable			0	1,740
Repayment of notes payable			(53,530)	(6,199)
Scheduled principal payments			(4,562)	(5,513)
Payment of loan costs			(3,343)	(9,432)
Early redemption costs			(10,647)	(10,491)
Net cash used in financing activities			(283,639)	(113,136)
Net decrease in cash and cash equivalents and restricted cash			(7,826)	(6,141)
Cash and cash equivalents and restricted cash at beginning of the period			45,190	49,381	$ 49,381
Cash and cash equivalents and restricted cash at end of the period	37,364	43,240	37,364	43,240	45,190
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $1,996 and $4,150 in 2019 and 2018, respectively)			68,351	66,692
Cash paid for income taxes, net of refunds			459	290
Supplemental disclosure of non-cash transactions:
Mortgage loans assumed for the acquisition of real estate				9,700
Change in accrued capital expenditures			9,149
Common stock issued by Parent Company for dividend reinvestment plan	357	320	740	678
Stock-based compensation capitalized			1,105	1,777
Contributions from limited partners in consolidated partnerships, net			66
Common stock issued for dividend reinvestment in trust			479	415
Contribution of stock awards into trust			2,397	1,174
Distribution of stock held in trust			167	524
Change in fair value of debt securities available-for-sale			260	(89)
Partnership Interest [Member]
Cash flows from operating activities:
Net income	52,690	48,589	144,183	102,054
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			190,783	177,629
Amortization of deferred loan costs and debt premiums			5,911	4,999
(Accretion) and amortization of above and below market lease intangibles, net			(19,496)	(19,326)
Stock-based compensation, net of capitalization			6,989	6,574
Equity in income of investments in real estate partnerships	(13,128)	(9,174)	(43,955)	(19,523)
Gain on sale of real estate, net of tax			(16,932)	(1,219)
Provision for impairment, net of tax	10,441	12,533	12,113	28,587
Early extinguishment of debt		11,010	10,591	11,172
Distribution of earnings from operations of investments in real estate partnerships			25,659	26,711
Settlement of derivative instruments			(5,719)	0
Deferred compensation expense			3,297	544
Realized and unrealized gain on investments			(3,299)	(530)
Changes in assets and liabilities:
Tenant and other receivables			6,975	(3,802)
Deferred leasing costs			(4,782)	(3,404)
Other assets			(7,628)	(6,174)
Accounts payable and other liabilities			(3,292)	(6,052)
Tenants’ security, escrow deposits and prepaid rent			(12,075)	2,666
Net cash provided by operating activities			289,323	300,906
Cash flows from investing activities:
Acquisition of operating real estate			(19,302)	(85,766)
Advance deposits paid on acquisition of operating real estate			(11,000)	(2,025)
Real estate development and capital improvements			(80,032)	(120,579)
Proceeds from sale of real estate investments			83,460	42,508
Issuance of notes receivable			0	15,648
Investments in real estate partnerships			(32,970)	(45,451)
Distributions received from investments in real estate partnerships			46,740	2,328
Dividends on investment securities			264	176
Acquisition of investment securities			(11,498)	(11,726)
Proceeds from sale of investment securities			10,828	10,976
Net cash used in investing activities			(13,510)	(193,911)
Cash flows from financing activities:
Repurchase of common shares in conjunction with equity award plans			(6,148)	(6,755)
Common shares repurchased through share repurchase program			(32,778)	(124,989)
Proceeds from sale of treasury stock			9	99
Distributions to limited partners in consolidated partnerships, net			(968)	(2,159)
Dividends paid to common stockholders			(195,655)	(188,948)
Repayment of fixed rate unsecured notes			(250,000)	(150,000)
Proceeds from issuance of fixed rate unsecured notes, net			298,983	299,511
Proceeds from unsecured credit facilities			185,000	400,000
Repayment of unsecured credit facilities			(210,000)	(310,000)
Proceeds from notes payable			0	1,740
Repayment of notes payable			(53,530)	(6,199)
Scheduled principal payments			(4,562)	(5,513)
Payment of loan costs			(3,343)	(9,432)
Early redemption costs			(10,647)	(10,491)
Net cash used in financing activities			(283,639)	(113,136)
Net decrease in cash and cash equivalents and restricted cash			(7,826)	(6,141)
Cash and cash equivalents and restricted cash at beginning of the period			45,190	49,381	49,381
Cash and cash equivalents and restricted cash at end of the period	$ 37,364	$ 43,240	37,364	43,240	$ 45,190
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $1,996 and $4,150 in 2019 and 2018, respectively)			68,351	66,692
Cash paid for income taxes, net of refunds			459	290
Supplemental disclosure of non-cash transactions:
Mortgage loans assumed for the acquisition of real estate				9,700
Change in accrued capital expenditures			9,149
Common stock issued by Parent Company for dividend reinvestment plan			740	678
Stock-based compensation capitalized			1,105	1,777
Contributions from limited partners in consolidated partnerships, net			66
Common stock issued for dividend reinvestment in trust			479	415
Contribution of stock awards into trust			2,397	1,174
Distribution of stock held in trust			167	524
Change in fair value of debt securities available-for-sale			$ 260	$ (89)