Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Cash Flows [Abstract]
Net income	$ 69,771	$ 23,092	$ 85,571
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	164,201	142,472	127,690
Other amortization	3,000	3,879	3,351
Share-based compensation	10,691	10,028	7,598
Amortization of straight-line rent receivable	(4,281)	(6,072)	(7,201)
Amortization of straight-line rent liability	1,519	1,497	67
Gain on sales of real estate assets	(41,665)	(39,524)	(41,044)
Loss on extinguishment of debt		44,985
Impairment of real estate assets		5,385	121
Equity from unconsolidated joint ventures (income)	(4)	(7)
Distributions from unconsolidated joint ventures	182
Provision for bad debts, net	60	159	(21)
Changes in operating assets and liabilities:
Other assets	(3,998)	(2,156)	(1,332)
Accounts payable and accrued liabilities	4,731	(7,307)	449
Other liabilities	4,148	3,335	(23,977)
Net cash provided by operating activities	208,355	179,766	151,272
INVESTING ACTIVITIES
Acquisitions of real estate	(104,312)	(274,668)	(224,944)
Development of real estate	(26,728)	(14,911)	(34,719)
Additional long-lived assets	(70,807)	(80,613)	(71,433)
Investment in unconsolidated joint ventures		(8,701)
Proceeds from sales of real estate	96,812	119,426	93,253
Proceeds from notes receivable repayments	8	19	19
Net cash used in investing activities	(105,027)	(259,448)	(237,824)
FINANCING ACTIVITIES
Net borrowings (repayments) on unsecured credit facility	73,000	82,000	(99,000)
Repayment on term loan			(50,000)
Repayments of notes and bonds payable		297,459	11,500
Repayments of notes and bonds payable	(19,850)	(5,829)	(37,910)
Redemption of notes and bonds payable		(442,774)
Dividends paid	(150,266)	(142,327)	(131,759)
Net proceeds from issuance of common stock	611	248,554	450,503
Common stock redemptions	(4,532)	(1,686)	(1,756)
Debt issuance and assumption costs	(125)	(4,007)	(4,621)
Net cash (used in) provided by financing activities	(101,162)	31,390	136,957
Increase (decrease) in cash, cash equivalents and restricted cash	2,166	(48,292)	50,405
Cash, cash equivalents and restricted cash at beginning of period	6,215	54,507	4,102
Cash, cash equivalents and restricted cash at end of period	8,381	6,215	54,507
Supplemental Cash Flow Information:
Interest paid	45,752	64,395	55,878
Mortgage notes payable assumed upon acquisition (adjusted to fair value)	7,995	43,674	13,951
Invoices accrued for construction, tenant improvements and other capitalized costs	12,682	8,303	11,734
Capitalized interest	$ 951	$ 871	$ 1,258