Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
OPERATING ACTIVITIES
Net income (loss)	$ 14,127	$ (5,473)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	86,349	77,728
Stock-based compensation	3,400	4,131
Straight-line rent receivable	(7,907)	(5,654)
Straight-line rent liability	522	311
Gain on sales of real estate properties	(3)	(21,970)
Loss on extinguishment of debt	0	29,907
Impairments	11,034	9,889
Provision for bad debt, net of recoveries	126	119
Changes in operating assets and liabilities:
Other assets	(16,231)	(5,988)
Accounts payable and accrued liabilities	(10,644)	(10,273)
Other liabilities	(3,123)	(788)
Net cash provided by operating activities	77,650	71,939
INVESTING ACTIVITIES
Acquisitions of real estate	(37,694)	(104,451)
Additional long-lived assets	(54,899)	(52,199)
Funding of mortgages	(1,244)	(57,780)
Proceeds from acquisition of real estate upon mortgage note receivable default	204	0
Proceeds from sales of real estate	6,134	75,855
Proceeds from mortgages and notes receivable repayments	5,618	643
Net cash used in investing activities	(81,881)	(137,932)
FINANCING ACTIVITIES
Net borrowings (repayments) on unsecured credit facility	(154,000)	75,000
Borrowings on term loan	200,000	0
Borrowings on notes and bonds payable	0	247,948
Repayments on notes and bonds payable	(4,415)	(18,655)
Redemption of notes and bonds payable	0	(371,839)
Dividends paid	(86,923)	(82,815)
Net proceeds from issuance of common stock	52,712	220,045
Common stock redemptions	(382)	(247)
Capital contributions received from noncontrolling interest holders	0	1,749
Distributions to noncontrolling interest holders	(380)	(32)
Purchase of noncontrolling interest	(8,189)	0
Debt issuance and assumption costs	(1,179)	(4,777)
Net cash provided by (used in) financing activities	(2,756)	66,377
Increase (decrease) in cash and cash equivalents	(6,987)	384
Cash and cash equivalents, beginning of period	8,671	6,776
Cash and cash equivalents, end of period	1,684	7,160
Supplemental Cash Flow Information:
Interest paid	59,227	62,326
Company-financed real estate property sales	1,900	4,241
Invoices accrued for construction, tenant improvement and other capitalized costs	4,662	6,291
Mortgage notes payable assumed upon acquisition (adjusted to fair value)	12,618	12,678
Capitalized interest	0	183
Elimination of construction mortgage note receivable upon acquisition real estate property	$ 0	$ 97,203