CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash Flows from Operating Activities
Net income	$ 20,781	$ 18,516	$ 15,756	$ 16,636	$ 58,020	$ 45,460
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,897		8,142		32,597	23,949
Amortization from above (below) lease intangibles, net	3,400		3,000		9,882	7,794
Amortization from financing and credit facility costs					966	768
Stock-based compensation					2,972	2,171
Provision for impairment	0		488		1,609	1,651
Settlement of interest rate swap					802
(Gain) loss on sale of assets					(8,973)	(10,949)
(Increase) decrease in accounts receivable					(4,468)	(5,122)
(Increase) decrease in other assets					47	(934)
Increase (decrease) in accounts payable, accrued expenses, and other liabilities					(4,911)	(536)
Net Cash Provided by Operating Activities					88,543	64,252
Cash Flows from Investing Activities
Acquisition of real estate investments and other assets					(568,523)	(352,085)
Development of real estate investments and other assets (including capitalized interest of $321 in 2019 and $381 in 2018)					(13,880)	(17,390)
Payment of leasing costs					(292)	(1,191)
Net proceeds from sale of assets					34,513	60,038
Net Cash Used in Investing Activities					(548,182)	(310,628)
Cash Flows from Financing Activities
Proceeds (costs) from common stock offerings, net					276,960	159,604
Repurchase of common shares					(1,400)	(1,142)
Unsecured revolving credit facility borrowings (repayments), net					229,000
Payments of mortgage notes payable					(2,650)	(26,915)
Unsecured term loan proceeds						125,000
Payments of unsecured term loans					(18,543)	(571)
Dividends paid					(66,102)	(49,018)
Distributions to Non-Controlling Interest					(582)	(549)
Payments for financing costs					(217)	(568)
Net Cash Provided by Financing Activities					416,466	205,841
Net Increase (Decrease) in Cash and Cash Equivalents					(43,173)	(40,535)
Cash and cash equivalents and cash held in escrow, beginning of period		$ 53,975		$ 58,782	53,975	58,782	$ 58,782
Cash and cash equivalents and cash held in escrow, end of period	$ 10,802		$ 18,247		10,802	18,247	$ 53,975
Supplemental Disclosure of Cash Flow Information
Cash paid for interest (net of amounts capitalized)					25,496	18,944
Cash paid for income tax					754	387
Supplemental Disclosure of Non-Cash Investing and Financing Activities
Operating lease right of use assets added upon implementation of leases standard on January 1, 2019					7,505
Additional operating lease right of use assets added under new ground leases after January 1, 2019					12,167
Operating lease right of use assets disposed of upon acquisition of underlying ground leased land					(3,059)
Dividends and limited partners' distributions declared and unpaid					24,353	18,808
Accrual of development, construction and other real estate investment costs					$ 7,331	$ 4,422