Properties, net (Details 4) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011 sqfeet Year property
Dispositions
Number of Buildings	8
Total Rentable Square Feet	254,000
Sale Price	$ 24,500
Gain on Sale	1,449
Towson Portfolio
Dispositions
Number of Buildings	4
Total Rentable Square Feet	179,000
Sale Price	16,000
Gain on Sale	1,124
216 Schilling Circle
Dispositions
Number of Buildings	1
Total Rentable Square Feet	36,000
Sale Price	4,700
Gain on Sale	175
1344 & 1348 Ashton Road and 1350 Dorsey Road
Dispositions
Number of Buildings	3
Total Rentable Square Feet	39,000
Sale Price	3,800
Gain on Sale	$ 150