Condensed Consolidated Statements of Operations (Unaudited) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Revenues:    
Rental and other property income $ 65,004 $ 60,983
Tenant reimbursement income 4,524 4,787
Earned income from direct financing leases 472 486
Interest income on mortgage notes receivable 1,565 1,621
Interest income on marketable securities   1,938
Total revenue 71,565 69,815
Expenses:    
General and administrative expenses 2,228 2,002
Property operating expenses 5,765 5,812
Property and asset management expenses 4,661 4,356
Acquisition related expenses 17 362
Depreciation 15,212 14,657
Amortization 6,982 7,397
Total operating expenses 34,865 34,586
Operating income 36,700 35,229
Other income (expense):    
Equity in income of unconsolidated joint ventures and other income 128 168
Gain on sale of marketable securities   7,859
Interest expense (27,025) (26,521)
Total other expense (26,897) (18,494)
Net income $ 9,803 $ 16,735
Weighted average number of common shares outstanding:    
Basic 210,176,186 209,271,540
Diluted 210,177,282 209,271,540
Net income per common share:    
Basic and diluted $ 0.05 $ 0.08
Distributions declared per common share:    
Basic and diluted $ 0.16 $ 0.15