Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 12,456	$ 51,700	$ 47,049
Adjustments to reconcile net earnings to net cash flow provided by operating activities:
Depreciation and amortization expense	10,336	9,738	11,027
Impairment charges	20,226		1,135
Gains on dispositions of real estate	(968)	(1,705)	(5,467)
Deferred rent receivable, net of allowance	(453)	96	(763)
Allowance for deferred rent and accounts receivable	28,879	229	120
Amortization of above-market and below-market leases	(685)	(1,260)	(1,217)
Accretion expense	899	775	884
Stock-based employee compensation expense	643	480	390
Changes in assets and liabilities:
Other receivables, net	228	408	(669)
Net investment in direct financing leases	505	(323)	(85)
Accounts receivable, net	(14,890)	(189)	(175)
Prepaid expenses and other assets	130	(483)	339
Environmental remediation costs	(1,981)	(2,512)	(1,676)
Accounts payable and accrued liabilities	5,905	(31)	1,640
Net cash flow provided by operating activities	61,230	56,923	52,532
CASH FLOWS FROM INVESTING ACTIVITIES:
Property acquisitions and capital expenditures	(167,495)	(4,725)	(55,317)
Proceeds from dispositions of real estate	3,385	2,858	6,939
(Increase) decrease in cash held for property acquisitions	(750)	2,665	(1,623)
Issuance of notes and mortgages receivable	(31,468)		(300)
Collection of notes and mortgages receivable	2,679	158	155
Net cash flow provided by (used in) investing activities	(193,649)	956	(50,146)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under credit agreement	247,253	163,500	79,000
Repayments under credit agreement	(140,853)	(273,400)	(58,050)
Borrowings under term loan agreement			24,500
Repayments under term loan agreement	(780)	(780)	(130)
Payments of cash dividends	(63,436)	(52,332)	(46,834)
Payments of loan origination costs	(175)
Net proceeds from issuance of common stock	91,986	108,205
Net cash flow provided by (used in) financing activities	133,995	(54,807)	(1,514)
Net increase in cash and cash equivalents	1,576	3,072	872
Cash and cash equivalents at beginning of year	6,122	3,050	2,178
Cash and cash equivalents at end of year	7,698	6,122	3,050
Supplemental disclosures of cash flow information
Interest paid	5,523	4,863	5,046
Income taxes paid, net	$ 267	$ 365	$ 467