Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
OPERATING ACTIVITIES
Net income (loss)	$ (5,473)	$ 11,897
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	77,728	74,688
Stock-based compensation	4,131	2,588
Straight-line rent receivable	(5,654)	(4,926)
Straight-line rent liability	311	312
Gain on sales of real estate properties	(21,970)	(9,696)
Loss on extinguishments of debt	29,907	0
Impairments	9,889	7,197
Provision for bad debt, net of recoveries	119	147
Changes in operating assets and liabilities:
Other assets	(5,988)	(3,051)
Accounts payable and accrued liabilities	(10,273)	(13,015)
Other liabilities	(788)	6,386
Net cash provided by operating activities	71,939	72,527
INVESTING ACTIVITIES
Acquisition of real estate	(104,451)	(24,019)
Development of real estate	0	(8,981)
Additional long-lived assets	(52,199)	(43,389)
Funding of mortgages	(57,780)	(54,264)
Proceeds from sales of real estate	75,855	64,866
Proceeds from mortgage repayment by previously consolidated VIE	0	35,057
Proceeds from mortgages and notes receivable repayments	643	11,931
Net cash used in investing activities	(137,932)	(18,799)
FINANCING ACTIVITIES
Net borrowings (repayments) on unsecured credit facility	75,000	(178,000)
Borrowings on notes and bonds payable	247,948	0
Repayments on notes and bonds payable	(18,655)	(3,678)
Redemption of notes and bonds payable	(371,839)	0
Dividends paid	(82,815)	(70,186)
Net proceeds from issuance of common stock	220,045	202,247
Common stock redemptions	(247)	(45)
Capital contributions received from noncontrolling interest holders	1,749	0
Distributions to noncontrolling interest holders	(32)	(20)
Debt issuance and assumption costs	(4,777)	(3)
Net cash provided by (used in) financing activities	66,377	(49,685)
Increase in cash and cash equivalents	384	4,043
Cash and cash equivalents, beginning of period	6,776	4,738
Cash and cash equivalents, end of period	7,160	8,781
Supplemental Cash Flow Information:
Interest paid	62,326	64,773
Capitalized interest	183	4,782
Company-financed real estate property sales	4,241	11,200
Invoices accrued for construction, tenant improvement and other capitalized costs	6,291	2,717
Mortgage notes payable assumed upon acquisition (adjusted to fair value)	12,678	0
Elimination of construction mortgage note receivable upon acquisition of underlying real estate property	97,203	0
Construction liabilities transferred upon deconsolidation of VIE	$ 0	$ 3,450