Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
OPERATING ACTIVITIES
Net income	$ 21,300	$ 23,298
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	63,280	60,250
Stock-based compensation	3,798	3,078
Straight-line rent receivable	(4,223)	(5,358)
Straight-line rent liability	368	389
Gain on sales of real estate assets	(8)	(41,606)
Loss on extinguishment of debt		27,998
Impairments of real estate properties	0	3,328
Pension termination	0	5,260
Impairment of internally-developed software	0	654
Provision for bad debts, net	39	(182)
Changes in operating assets and liabilities:
Other assets	3,139	(3,784)
Accounts payable and accrued liabilities	(7,927)	(6,424)
Other liabilities	(20,287)	891
Net cash provided by operating activities	59,479	67,792
INVESTING ACTIVITIES
Acquisitions of real estate	(63,172)	(43,017)
Development of real estate	(18,982)	(6,027)
Additional long-lived assets	(29,286)	(25,584)
Proceeds from sales of real estate	0	94,463
Proceeds from mortgages and notes receivable repayments	9	9
Net cash (used in) provided by investing activities	(111,431)	19,844
FINANCING ACTIVITIES
Net borrowings (repayments) on unsecured credit facility	(16,000)	73,000
Borrowings on notes and bonds payable	11,500	249,793
Repayments on notes and bonds payable	(19,963)	(48,438)
Redemption of notes and bonds payable		(333,222)
Dividends paid	(62,239)	(59,954)
Net proceeds from issuance of common stock	145,125	40,366
Common stock redemptions	(1,282)	(271)
Settlement of swaps		(1,684)
Debt issuance and assumption costs	(265)	(2,314)
Net cash provided by (used in) financing activities	56,876	(82,724)
Increase in cash and cash equivalents	4,924	4,912
Cash and cash equivalents, beginning of period	4,102	3,519
Cash and cash equivalents, end of period	9,026	8,431
Supplemental Cash Flow Information:
Interest paid	28,692	40,533
Invoices accrued for construction, tenant improvement and other capitalized costs	12,745	4,960
Mortgage notes payable assumed upon acquisition (adjusted to fair value)	13,951	9,721
Capitalized interest	$ 452	$ 33