Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Proceeds from Issuance of Unsecured Debt	$ 646,424
Cash flows from operating activities:
Net income	20,715	$ (53,577)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income of investments in real estate partnerships	28,251
Provision for impairment	0	(866)
Changes in assets and liabilities:
Net cash provided by operating activities	32,723
Cash flows from investing activities:
Acquisition of operating real estate	(648,957)
Real estate development and capital improvements	(66,504)
Proceeds from sale of real estate investments	1,749	34,321
Payments for (Proceeds from) Loans Receivable	510
Investments in real estate partnerships	(1,688)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	25,428
Dividends on investment securities	55
Acquisition of securities	(3,334)
Proceeds from sale of securities	3,815
Net cash used in investing activities	(689,946)
Cash flows from financing activities:
Proceeds from sale of treasury stock	76
Distributions to limited partners in consolidated partnerships, net	(786)
Distributions to exchangeable operating partnership unit holders	(79)
Dividends paid to common stockholders	(53,289)
Dividends paid to preferred stockholders	(3,241)
Proceeds from unsecured credit facilities	740,000
Repayment of unsecured credit facilities	(360,000)
Proceeds from notes payable	1,577
Repayments of Notes Payable	(11,422)
Scheduled principal payments	(1,367)
Payment of loan costs	(8,796)
Net cash provided by (used in) financing activities	680,822
Payments for Repurchase of Common Stock	(18,275)
Payments for Repurchase of Preferred Units	250,000
Cash and cash equivalents at beginning of the period	13,256
Cash and cash equivalents at end of the period	36,855
Net increase (decrease) in cash and cash equivalents	23,599
Parent Company [Member]
Proceeds from Issuance of Unsecured Debt	646,424	0
Cash flows from operating activities:
Net income	20,715	(53,577)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	60,053	38,716
Amortization of deferred loan cost and debt premium	2,459	2,353
(Accretion) and amortization of above and below market lease intangibles, net	(3,484)	(351)
Share-based Compensation	12,131	2,621
Stock-based compensation, net of capitalization	778	814
Equity in income of investments in real estate partnerships	(9,342)	(12,920)
Gain on sale of real estate, net of tax	(415)	(12,868)
Provision for impairment	0	(1,666)
(Payments for) Proceeds from Settlement of Derivative Instrument	(87)	0
Distribution of earnings from operations of investments in real estate partnerships	(12,784)	(13,840)
Deferred compensation expense	1,062	(148)
Realized and unrealized (gain) loss on investments	(1,064)	155
Increase (Decrease) in Restricted Cash for Operating Activities	(67)	109
Changes in assets and liabilities:
Accounts receivable, net	8,974	4,371
Straight-line rent receivables, net	(3,439)	(1,848)
Deferred leasing costs	(1,355)	(2,903)
Other assets	(2,657)	(746)
Accounts payable and other liabilities	(24,370)	(7,286)
Tenants’ security, escrow deposits and prepaid rent	2,121	(1,301)
Net cash provided by operating activities	32,723	76,819
Cash flows from investing activities:
Acquisition of operating real estate	0	(16,483)
Payments for Merger Related Costs	(648,957)	0
Real estate development and capital improvements	(66,504)	(38,289)
Proceeds from sale of real estate investments	1,749	32,261
Payments for (Proceeds from) Loans Receivable	510	0
Investments in real estate partnerships	(1,688)	(2,438)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	25,428	18,296
Dividends on investment securities	55	59
Acquisition of securities	(3,334)	(41,946)
Proceeds from sale of securities	3,815	41,207
Net cash used in investing activities	(689,946)	(7,333)
Cash flows from financing activities:
Net proceeds from common stock issuance	0	12,293
Proceeds from sale of treasury stock	76	904
Distributions to limited partners in consolidated partnerships, net	(786)	(1,707)
Distributions to exchangeable operating partnership unit holders	(79)	(77)
Dividends paid to common stockholders	(53,289)	(48,510)
Dividends paid to preferred stockholders	(3,241)	(5,266)
Proceeds from unsecured credit facilities	740,000	10,000
Repayment of unsecured credit facilities	(360,000)	(10,000)
Proceeds from notes payable	1,577	0
Repayments of Notes Payable	(11,422)	(27,281)
Scheduled principal payments	(1,367)	(1,572)
Payment of loan costs	(8,796)	(5)
Net cash provided by (used in) financing activities	680,822	(79,205)
Payments Related to Tax Withholding for Share-based Compensation	(18,275)	(7,984)
Payments for Repurchase of Preferred Units	250,000	0
Cash and cash equivalents at beginning of the period	13,256	36,856
Cash and cash equivalents at end of the period	36,855	27,137
Net increase (decrease) in cash and cash equivalents	23,599	(9,719)
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $1,061 and $973 in 2017 and 2016, respectively)	7,687	7,611
Supplemental disclosure of non-cash transactions:
Common stock issued under dividend reinvestment plan	301	292
Contributions from limited partners in consolidated partnerships, net	100	8,362
Common stock issued for dividend reinvestment in trust	177	190
Contribution of stock awards into trust	929	958
Distribution of stock held in trust	4,114	1,807
Unrealized Gain (Loss) on Securities	32	(36)
Deconsolidation of previously consolidated partnership [Abstract]
Deconsolidation of consolidated partnership, Real estate, net	5,985,895	0
Deconsolidation of consolidated partnership, Return of capital	103,566	0
Deconsolidation of consolidated partnership, Mortgage Notes Payable	(757,399)	0
Deconsolidation of consolidated partnership, Other assets and liabilities	(80,693)	0
Deconsolidation of consolidated partnership, Noncontrolling Interest	(4,471,808)	0
Partnership Interest [Member]
Proceeds from Issuance of Unsecured Debt	646,424	0
Cash flows from operating activities:
Net income	20,715	(53,577)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	60,053	38,716
Amortization of deferred loan cost and debt premium	2,459	2,353
(Accretion) and amortization of above and below market lease intangibles, net	(3,484)	(351)
Share-based Compensation	12,131	2,621
Stock-based compensation, net of capitalization	778	814
Equity in income of investments in real estate partnerships	(9,342)	(12,920)
Gain on sale of real estate, net of tax	(415)	(12,868)
Provision for impairment	0	(1,666)
(Payments for) Proceeds from Settlement of Derivative Instrument	(87)	0
Distribution of earnings from operations of investments in real estate partnerships	(12,784)	(13,840)
Deferred compensation expense	1,062	(148)
Realized and unrealized (gain) loss on investments	(1,064)	155
Increase (Decrease) in Restricted Cash for Operating Activities	(67)	109
Changes in assets and liabilities:
Accounts receivable, net	8,974	4,371
Straight-line rent receivables, net	(3,439)	(1,848)
Deferred leasing costs	(1,355)	(2,903)
Other assets	(2,657)	(746)
Accounts payable and other liabilities	(24,370)	(7,286)
Tenants’ security, escrow deposits and prepaid rent	2,121	(1,301)
Net cash provided by operating activities	32,723	76,819
Cash flows from investing activities:
Acquisition of operating real estate	0	(16,483)
Payments for Merger Related Costs	(648,957)	0
Real estate development and capital improvements	(66,504)	(38,289)
Proceeds from sale of real estate investments	1,749	32,261
Payments for (Proceeds from) Loans Receivable	510	0
Investments in real estate partnerships	(1,688)	(2,438)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	25,428	18,296
Dividends on investment securities	55	59
Acquisition of securities	(3,334)	(41,946)
Proceeds from sale of securities	3,815	41,207
Net cash used in investing activities	(689,946)	(7,333)
Cash flows from financing activities:
Net proceeds from common units issued as a result of common stock issued by Parent Company	0	12,293
Proceeds from sale of treasury stock	76	904
Distributions to limited partners in consolidated partnerships, net	(786)	(1,707)
Dividends paid to common stockholders	(53,368)	(48,587)
Dividends paid to preferred stockholders	(3,241)	(5,266)
Proceeds from unsecured credit facilities	740,000	10,000
Repayment of unsecured credit facilities	(360,000)	(10,000)
Proceeds from notes payable	1,577	0
Repayments of Notes Payable	(11,422)	(27,281)
Scheduled principal payments	(1,367)	(1,572)
Payment of loan costs	(8,796)	(5)
Net cash provided by (used in) financing activities	680,822	(79,205)
Payments for Repurchase of Common Stock	(18,275)	(7,984)
Payments for Repurchase of Preferred Units	250,000	0
Cash and cash equivalents at beginning of the period	13,256	36,856
Cash and cash equivalents at end of the period	36,855	27,137
Net increase (decrease) in cash and cash equivalents	23,599	(9,719)
Supplemental disclosure of cash flow information:
Cash paid for interest (net of capitalized interest of $1,061 and $973 in 2017 and 2016, respectively)	7,687	7,611
Supplemental disclosure of non-cash transactions:
Common stock issued under dividend reinvestment plan	301	292
Contributions from limited partners in consolidated partnerships, net	100	8,362
Common stock issued for dividend reinvestment in trust	177	190
Contribution of stock awards into trust	929	958
Distribution of stock held in trust	4,114	1,807
Unrealized Gain (Loss) on Securities	32	(36)
Deconsolidation of previously consolidated partnership [Abstract]
Deconsolidation of consolidated partnership, Real estate, net	5,985,895	0
Deconsolidation of consolidated partnership, Return of capital	103,566	0
Deconsolidation of consolidated partnership, Mortgage Notes Payable	(757,399)	0
Deconsolidation of consolidated partnership, Other assets and liabilities	(80,693)	0
Deconsolidation of consolidated partnership, Noncontrolling Interest	$ (4,471,808)	$ 0