Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Document Fiscal Year Focus	2016
Cash flows from operating activities:
Net income	$ 166,992	$ 152,543	$ 188,847
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income of investments in real estate partnerships	(56,518)	(22,508)	(31,270)
Provision for impairment	1,700
Cash flows from investing activities:
Proceeds from sale of real estate investments	137,479	108,822	118,787
Cash flows from financing activities:
Dividends, Preferred Stock, Cash	21,062	21,062	21,062
Parent Company [Member]
Cash flows from operating activities:
Net income	166,992	152,543	188,847
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	162,327	146,829	147,791
Amortization of deferred loan cost and debt premium	9,762	9,677	10,521
Amortization and (accretion) of above and below market lease intangibles, net	(3,879)	(1,598)	(3,101)
Stock-based compensation, net of capitalization	10,652	11,081	9,662
Equity in income of investments in real estate partnerships	(56,518)	(22,508)	(31,270)
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	0	0	18,271
Gain Loss On Sale Of Properties Including Discontinued Operations	(47,321)	(35,606)	(55,077)
Provision for impairment	4,200	0	1,257
Early extinguishment of debt	14,240	8,239	18
Proceeds from Equity Method Investment, Dividends or Distributions	50,361	46,646	42,767
(Payments for) Proceeds from Settlement of Derivative Instrument	0	(7,267)	4,648
Gain on derivative instruments	0	0	(13)
Deferred compensation expense	1,655	207	1,386
Net Realized and Unrealized Gain (Loss) on Trading Securities	1,673	626	9,158
Changes in assets and liabilities:
Increase (Decrease) in Restricted Cash for Operating Activities	59	1,926	848
Accounts receivable, net	(9,565)	(11,965)	(6,225)
Straight-line rent receivable, net	(7,219)	(8,231)	(6,544)
Deferred leasing costs	(10,349)	(12,949)	(8,252)
Other assets	673	(496)	89
Accounts payable and other liabilities	5,543	(3,810)	6,201
Tenants’ security and escrow deposits and prepaid rent	(564)	3,545	1,618
Net cash provided by operating activities	289,376	275,637	277,742
Cash flows from investing activities:
Acquisition of operating real estate	(333,220)	(42,983)	(112,120)
Payments for (Proceeds from) Deposits on Real Estate Acquisitions	750	2,250	0
Real estate development and capital improvements	(234,598)	(205,103)	(238,237)
Proceeds from sale of real estate investments	135,269	108,822	118,787
Payments for (Proceeds from) Loans Receivable	0	1,719	0
Investments in real estate partnerships	(37,879)	(20,054)	(23,577)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	58,810	23,801	37,152
Payments for (Proceeds from) Other Investing Activities	330	243	243
Acquisition of securities	(55,223)	(31,941)	(23,760)
Proceeds from sale of securities	57,590	28,400	31,222
Net cash used in investing activities	(409,671)	(139,346)	(210,290)
Cash flows from financing activities:
Proceeds from Issuance of Common Stock	548,920	198,494	102,453
Proceeds from sale of treasury stock	957	0	0
Payments for Repurchase of Common Stock	29	0	0
Redemption of preferred stock and partnership units	0	0	(300)
Proceeds from (Payments to) Noncontrolling Interests	(4,213)	(5,341)	(5,303)
Payments of Ordinary Dividends, Noncontrolling Interest	(307)	(299)	(300)
Dividends paid to common stockholders	(201,029)	(181,392)	(172,600)
Dividends paid to preferred stockholders	(21,062)	(21,062)	(21,062)
Dividends, Preferred Stock, Cash	21,062	21,062	21,062
Repayment of fixed rate unsecured notes	(300,000)	(450,000)	(150,000)
Proceeds from Issuance of Unsecured Debt	0	248,160	248,705
Proceeds from unsecured credit facilities	460,000	445,000	255,000
Repayment of unsecured credit facilities	(345,000)	(355,000)	(255,000)
Proceeds from notes payable	53,446	4,316	12,739
Repayment of notes payable	(72,803)	(76,168)	(38,717)
Repayments of Secured Debt	5,860	5,878	6,909
Payment of loan costs	(2,233)	(5,998)	(3,066)
Payments of Debt Extinguishment Costs	(14,092)	(8,043)	0
Net cash provided by (used in) financing activities	96,695	(213,211)	(34,360)
Net decrease in cash and cash equivalents	(23,600)	(76,920)	33,092
Cash and cash equivalents at beginning of the period	36,856	113,776	80,684
Cash and cash equivalents at end of the period	13,256	36,856	113,776
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $000, $6,078, and $3,686 in 2014, 2013, and 2012, respectively)	82,950	101,527	109,425
Income Taxes Paid	0	1,015	2,169
Supplemental disclosure of non-cash transactions:
Stock Issued During Period, Value, Conversion of Units	0	0	137
Mortgage loans assumed for the acquisition of real estate	0	42,799	103,187
Unrealized Gain (Loss) on Securities	24	(43)	0
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	0	0	15,385
Acquisition of previously unconsolidated real estate	0	0	16,182
Change in fair value of derivative instruments	(10,332)	(9,012)	(49,968)
Stock Issued During Period, Value, Dividend Reinvestment Plan	1,070	1,250	1,184
Contributions from limited partners in consolidated partnerships, net	8,755	13	1,579
Common stock issued for dividend reinvestment in trust	728	833	779
Stock-based compensation capitalized	2,963	2,988	2,707
Contribution of stock awards into trust	1,538	1,651	1,881
Distribution of stock held in trust	4,114	1,898	4
Deconsolidation of consolidated partnership, Real estate, net	14,144	0	0
Deconsolidation of consolidated partnership, Return of capital	(3,355)	0	0
Deconsolidation of consolidated partnership, Mortgage Notes Payable	(9,415)	0	0
Deconsolidation of consolidated partnership, Other assets and liabilities	571	0	0
Deconsolidation of consolidated partnership, Noncontrolling Interest	(2,099)	0	0
Partnership Interest [Member]
Cash flows from operating activities:
Net income	166,992	152,543	188,847
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	162,327	146,829	147,791
Amortization of deferred loan cost and debt premium	9,762	9,677	10,521
Amortization and (accretion) of above and below market lease intangibles, net	(3,879)	(1,598)	(3,101)
Stock-based compensation, net of capitalization	10,652	11,081	9,662
Equity in income of investments in real estate partnerships	(56,518)	(22,508)	(31,270)
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	0	0	18,271
Gain Loss On Sale Of Properties Including Discontinued Operations	(47,321)	(35,606)	(55,077)
Provision for impairment	4,200	0	1,257
Early extinguishment of debt	14,240	8,239	18
Deferred income tax expense (benefit) of taxable REIT subsidiary	0	0	0
Proceeds from Equity Method Investment, Dividends or Distributions	50,361	46,646	42,767
(Payments for) Proceeds from Settlement of Derivative Instrument	0	(7,267)	4,648
Gain on derivative instruments	0	0	(13)
Deferred compensation expense	1,655	207	1,386
Net Realized and Unrealized Gain (Loss) on Trading Securities	1,673	626	9,158
Changes in assets and liabilities:
Increase (Decrease) in Restricted Cash for Operating Activities	59	1,926	848
Accounts receivable, net	(9,565)	(11,965)	(6,225)
Straight-line rent receivable, net	(7,219)	(8,231)	(6,544)
Deferred leasing costs	(10,349)	(12,949)	(8,252)
Other assets	673	(496)	89
Accounts payable and other liabilities	5,543	(3,810)	6,201
Tenants’ security and escrow deposits and prepaid rent	(564)	3,545	1,618
Net cash provided by operating activities	289,376	275,637	277,742
Cash flows from investing activities:
Acquisition of operating real estate	(333,220)	(42,983)	(112,120)
Payments for (Proceeds from) Deposits on Real Estate Acquisitions	750	2,250	0
Real estate development and capital improvements	(234,598)	(205,103)	(238,237)
Proceeds from sale of real estate investments	135,269	108,822	118,787
Payments for (Proceeds from) Loans Receivable	0	1,719	0
Investments in real estate partnerships	(37,879)	(20,054)	(23,577)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	58,810	23,801	37,152
Payments for (Proceeds from) Other Investing Activities	330	243	243
Acquisition of securities	(55,223)	(31,941)	(23,760)
Proceeds from sale of securities	57,590	28,400	31,222
Net cash used in investing activities	(409,671)	(139,346)	(210,290)
Cash flows from financing activities:
Net proceeds from common units issued as a result of common stock issued by Parent Company	548,920	198,494	102,453
Proceeds from sale of treasury stock	957	0	0
Payments for Repurchase of Common Stock	29	0	0
Redemption of preferred stock and partnership units	0	0	(300)
Proceeds from (Payments to) Noncontrolling Interests	(4,213)	(5,341)	(5,303)
Dividends paid to common stockholders	(201,336)	(181,691)	(172,900)
Dividends paid to preferred stockholders	(21,062)	(21,062)	(21,062)
Repayment of fixed rate unsecured notes	(300,000)	(450,000)	(150,000)
Proceeds from Issuance of Unsecured Debt	0	248,160	248,705
Proceeds from unsecured credit facilities	460,000	445,000	255,000
Repayment of unsecured credit facilities	(345,000)	(355,000)	(255,000)
Proceeds from notes payable	53,446	4,316	12,739
Repayment of notes payable	(72,803)	(76,168)	(38,717)
Repayments of Secured Debt	5,860	5,878	6,909
Payment of loan costs	(2,233)	(5,998)	(3,066)
Payments of Debt Extinguishment Costs	(14,092)	(8,043)	0
Net cash provided by (used in) financing activities	96,695	(213,211)	(34,360)
Net decrease in cash and cash equivalents	(23,600)	(76,920)	33,092
Cash and cash equivalents at beginning of the period	36,856	113,776	80,684
Cash and cash equivalents at end of the period	13,256	36,856	113,776
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $000, $6,078, and $3,686 in 2014, 2013, and 2012, respectively)	82,950	101,527	109,425
Supplemental disclosure of non-cash transactions:
Stock Issued During Period, Value, Conversion of Units	0	0	137
Mortgage loans assumed for the acquisition of real estate	0	42,799	103,187
Unrealized Gain (Loss) on Securities	24	(43)	0
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	0	0	15,385
Acquisition of previously unconsolidated real estate	0	0	16,182
Change in fair value of derivative instruments	(10,332)	(9,012)	(49,968)
Stock Issued During Period, Value, Dividend Reinvestment Plan	1,070	1,250	1,184
Contributions from limited partners in consolidated partnerships, net	8,755	13	1,579
Common stock issued for dividend reinvestment in trust	728	833	779
Stock-based compensation capitalized	2,963	2,988	2,707
Contribution of stock awards into trust	1,538	1,651	1,881
Distribution of stock held in trust	4,114	1,898	4
Deconsolidation of consolidated partnership, Real estate, net	14,144	0	0
Deconsolidation of consolidated partnership, Return of capital	(3,355)	0	0
Deconsolidation of consolidated partnership, Mortgage Notes Payable	(9,415)	0	0
Deconsolidation of consolidated partnership, Other assets and liabilities	571	0	0
Deconsolidation of consolidated partnership, Noncontrolling Interest	(2,099)	0	0
Common Stock | Parent Company [Member]
Cash flows from financing activities:
Proceeds from Issuance of Common Stock			102,453
Supplemental disclosure of non-cash transactions:
Stock Issued During Period, Value, Conversion of Units			0
Stock Issued During Period, Value, Dividend Reinvestment Plan	$ 1,070	$ 1,250	$ 1,184