Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
OPERATING ACTIVITIES
Net income	$ 33,134	$ 50,778
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	96,145	90,000
Stock-based compensation	5,649	4,558
Straight-line rent receivable	(5,446)	(7,671)
Straight-line rent liability	(93)	583
Gain on sales of real estate assets	(8)	(58,092)
Loss on extinguishment of debt		27,998
Impairment of real estate assets	0	3,638
Pension termination	0	5,260
Impairment of internally-developed software	0	654
Provision for bad debts, net	(8)	(203)
Changes in operating assets and liabilities:
Other assets	(1,436)	(2,502)
Accounts payable and accrued liabilities	(3,889)	(2,285)
Other liabilities	(21,628)	594
Net cash provided by operating activities	102,420	113,310
INVESTING ACTIVITIES
Acquisitions of real estate	(162,702)	(70,043)
Development of real estate	(28,508)	(10,165)
Additional long-lived assets	(49,794)	(35,709)
Proceeds from sales of real estate	0	134,432
Proceeds from mortgages and notes receivable repayments	14	1,914
Net cash (used in) provided by investing activities	(240,990)	20,429
FINANCING ACTIVITIES
Net (repayments) borrowings on unsecured credit facility	(125,000)	57,000
Repayment on term loan	(50,000)
Borrowings of mortgage note payable	11,500	249,793
Repayments on notes and bonds payable	(36,786)	(49,632)
Redemption of notes and bonds payable		(333,222)
Dividends paid	(96,998)	(90,078)
Net proceeds from issuance of common stock	450,304	41,757
Common stock redemptions	(1,282)	(271)
Settlement of swaps		(1,684)
Debt issuance and assumption costs	(4,621)	(2,424)
Net cash provided by (used in) financing activities	147,117	(128,761)
Increase in cash and cash equivalents	8,547	4,978
Cash and cash equivalents, beginning of period	4,102	3,519
Cash and cash equivalents, end of period	12,649	8,497
Supplemental Cash Flow Information:
Interest paid	43,879	55,995
Invoices accrued for construction, tenant improvements and other capitalized costs	10,014	8,924
Mortgage notes payable assumed upon acquisition (adjusted to fair value)	13,951	19,431
Capitalized interest	$ 828	$ 113