Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net (loss) income	$ (24,783)	$ 91,493
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	89,295	97,194
Amortization of deferred loan costs and debt premiums	2,619	2,921
(Accretion) and amortization of above and below market lease intangibles, net	(12,460)	(13,090)
Stock-based compensation, net of capitalization	3,320	3,475
Equity in income of investments in real estate partnerships	(11,418)	(30,828)
Gain on sale of real estate, net of tax	(38,005)	(16,490)
Provision for impairment of real estate, net of tax	784	1,672
Goodwill impairment	132,128	0
Early extinguishment of debt	0	10,591
Distribution of earnings from investments in real estate partnerships	16,440	14,417
Settlement of derivative instruments	0	(5,719)
Deferred compensation expense	(4,328)	2,314
Realized and unrealized gain on investments	4,923	(2,354)
Changes in assets and liabilities:
Tenant and other receivables	18,569	9,050
Deferred leasing costs	(1,352)	(2,491)
Other assets	(12,201)	(11,212)
Accounts payable and other liabilities	(27,498)	(8,908)
Tenants’ security, escrow deposits and prepaid rent	(10,355)	(10,671)
Net cash provided by operating activities	125,678	131,364
Cash flows from investing activities:
Acquisition of operating real estate	(16,867)	(15,722)
Advance deposits refunded (paid) on acquisition of operating real estate	100	(1,250)
Real estate development and capital improvements	(56,309)	(39,929)
Proceeds from sale of real estate investments	103,522	82,533
Issuance of notes receivable	(167)	0
Investments in real estate partnerships	(32,972)	(19,587)
Return of capital from investments in real estate partnerships	0	41,587
Dividends on investment securities	84	116
Acquisition of investment securities	(4,392)	(5,359)
Proceeds from sale of investment securities	4,448	4,612
Net cash (used in) provided by investing activities	(2,553)	47,001
Cash flows from financing activities:
Net proceeds from common stock issuance	125,773	0
Repurchase of common shares in conjunction with equity award plans	(5,298)	(6,148)
Common shares repurchased through share repurchase program	0	(32,778)
Proceeds from sale of treasury stock	49	8
Distributions to limited partners in consolidated partnerships, net	(1,064)	(1,485)
Distributions to exchangeable operating partnership unit holders	(455)	(204)
Dividends paid to common stockholders	(99,409)	(97,608)
Repayment of fixed rate unsecured notes	0	(250,000)
Proceeds from issuance of fixed rate unsecured notes, net	0	298,983
Proceeds from unsecured credit facilities	610,000	110,000
Repayment of unsecured credit facilities	(125,000)	(145,000)
Repayment of notes payable	(3,891)	(40,315)
Scheduled principal payments	(2,547)	(2,235)
Payment of loan costs	0	(3,342)
Early redemption costs	0	(10,647)
Net cash provided by (used in) financing activities	498,158	(180,771)
Net increase (decrease) in cash and cash equivalents and restricted cash	621,283	(2,406)
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	736,845	42,784	115,562
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $1,175 and $1,015 in 2020 and 2019, respectively)	47,912	42,421
Cash paid for income taxes, net of refunds	317	15
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	4,942	10,494
Common stock issued under dividend reinvestment plan	379	383
Stock-based compensation capitalized	554	573
Contributions from limited partners in consolidated partnerships, net		881
Common stock issued for dividend reinvestment in trust	265	238
Contribution of stock awards into trust	862	1,328
Distribution of stock held in trust	390	167
Change in fair value of securities	577	174
Partnership Interest [Member]
Cash flows from operating activities:
Net (loss) income	(24,783)	91,493
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	89,295	97,194
Amortization of deferred loan costs and debt premiums	2,619	2,921
(Accretion) and amortization of above and below market lease intangibles, net	(12,460)	(13,090)
Stock-based compensation, net of capitalization	3,320	3,475
Equity in income of investments in real estate partnerships	(11,418)	(30,828)
Gain on sale of real estate, net of tax	(38,005)	(16,490)
Provision for impairment of real estate, net of tax	784	1,672
Goodwill impairment	132,128	0
Early extinguishment of debt	0	10,591
Distribution of earnings from investments in real estate partnerships	16,440	14,417
Settlement of derivative instruments	0	(5,719)
Deferred compensation expense	(4,328)	2,314
Realized and unrealized gain on investments	4,923	(2,354)
Changes in assets and liabilities:
Tenant and other receivables	18,569	9,050
Deferred leasing costs	(1,352)	(2,491)
Other assets	(12,201)	(11,212)
Accounts payable and other liabilities	(27,498)	(8,908)
Tenants’ security, escrow deposits and prepaid rent	(10,355)	(10,671)
Net cash provided by operating activities	125,678	131,364
Cash flows from investing activities:
Acquisition of operating real estate	(16,867)	(15,722)
Advance deposits refunded (paid) on acquisition of operating real estate	100	(1,250)
Real estate development and capital improvements	(56,309)	(39,929)
Proceeds from sale of real estate investments	103,522	82,533
Issuance of notes receivable	(167)	0
Investments in real estate partnerships	(32,972)	(19,587)
Return of capital from investments in real estate partnerships	0	41,587
Dividends on investment securities	84	116
Acquisition of investment securities	(4,392)	(5,359)
Proceeds from sale of investment securities	4,448	4,612
Net cash (used in) provided by investing activities	(2,553)	47,001
Cash flows from financing activities:
Net proceeds from common stock issuance	125,773	0
Repurchase of common shares in conjunction with equity award plans	(5,298)	(6,148)
Common shares repurchased through share repurchase program	0	(32,778)
Proceeds from sale of treasury stock	49	8
Distributions to limited partners in consolidated partnerships, net	(1,064)	(1,485)
Dividends paid to common stockholders	(99,864)	(97,812)
Repayment of fixed rate unsecured notes	0	(250,000)
Proceeds from issuance of fixed rate unsecured notes, net	0	298,983
Proceeds from unsecured credit facilities	610,000	110,000
Repayment of unsecured credit facilities	(125,000)	(145,000)
Repayment of notes payable	(3,891)	(40,315)
Scheduled principal payments	(2,547)	(2,235)
Payment of loan costs	0	(3,342)
Early redemption costs	0	(10,647)
Net cash provided by (used in) financing activities	498,158	(180,771)
Net increase (decrease) in cash and cash equivalents and restricted cash	621,283	(2,406)
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	736,845	42,784	$ 115,562
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $1,175 and $1,015 in 2020 and 2019, respectively)	47,912	42,421
Cash paid for income taxes, net of refunds	317	15
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	4,942	10,494
Common stock issued under dividend reinvestment plan	379	383
Stock-based compensation capitalized	554	573
Contributions from limited partners in consolidated partnerships, net		881
Common stock issued for dividend reinvestment in trust	265	238
Contribution of stock awards into trust	862	1,328
Distribution of stock held in trust	390	167
Change in fair value of securities	$ 577	$ 174