Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
OPERATING ACTIVITIES
Net income (loss)	$ (25,256)	$ 6,062
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	51,625	49,762
Stock-based compensation	2,985	1,653
Straight-line rent receivable	(3,492)	(3,445)
Straight-line rent liability	204	202
Gain on sales of real estate properties	(1,783)	(3,431)
Loss on extinguishments of debt	29,907	0
Impairments	3,630	4,336
Provision for bad debt, net of recoveries	7	108
Changes in operating assets and liabilities:
Other assets	(4,060)	4,050
Accounts payable and accrued liabilities	(8,806)	(9,573)
Other liabilities	(1,406)	3,073
Net cash provided by operating activities	43,555	52,797
INVESTING ACTIVITIES
Acquisition of real estate	(34,591)	(31,160)
Development of real estate	0	(23,764)
Additional long-lived assets	(34,305)	(6,598)
Funding of mortgages	(45,908)	(28,550)
Proceeds from sales of real estate	12,239	36,109
Proceeds from mortgage repayment by previously consolidated VIE	0	35,057
Proceeds from mortgages and notes receivable repayments	68	9,232
Net cash used in investing activities	(102,497)	(9,674)
FINANCING ACTIVITIES
Net borrowings on unsecured credit facility	120,000	4,000
Borrowings on notes and bonds payable	247,948	0
Repayments on notes and bonds payable	(17,480)	(2,436)
Redemption of notes and bonds payable	(371,839)	0
Dividends paid	(54,061)	(46,785)
Net proceeds from issuance of common stock	132,416	511
Common stock redemptions	(246)	(45)
Capital contributions received from noncontrolling interest holders	1,388	0
Distributions to noncontrolling interest holders	(32)	0
Debt issuance and assumption costs	(4,776)	(3)
Net cash provided by (used in) financing activities	53,318	(44,758)
Decrease in cash and cash equivalents	(5,624)	(1,635)
Cash and cash equivalents, beginning of period	6,776	4,738
Cash and cash equivalents, end of period	1,152	3,103
Supplemental Cash Flow Information:
Interest paid	38,057	38,307
Capitalized interest	171	3,469
Company-financed real estate property sales	4,241	11,200
Invoices accrued for construction, tenant improvement and other capitalized costs	6,011	5,931
Construction liabilities transferred upon deconsolidation of VIE	$ 0	$ 3,450