Real Estate Investments (Assets And Liabilities Assumed) (Details) (USD $)	9 Months Ended			0 Months Ended					9 Months Ended
	Sep. 30, 2012 property	Sep. 30, 2011	Sep. 30, 2012 In-Place Leases [Member]	Jul. 03, 2012 Property in Havertown, PA [Member]	Sep. 30, 2012 Contributor [Member] ARC Real Estate Partners, LLC [Member] property	Sep. 30, 2012 Occupied [Member] property	Sep. 30, 2012 Vacant [Member] Real Estate [Member] property	Dec. 31, 2011 Vacant [Member] Real Estate [Member] property	Sep. 30, 2012 Building [Member]	Sep. 30, 2012 Furniture and Fixtures [Member]	Sep. 30, 2012 Building Improvements [Member]
Real Estate Properties [Line Items]
Land	$ 10,228,000
Buildings, fixtures and improvements	75,360,000
Total tangible assets	85,588,000
Acquired intangibles			13,262,000
Purchase proce of acquired real estate investments	98,850,000
OP units issued to acquire real estate investments	(6,352,000)	0
Cash paid for acquired real estate investments	92,498,000	0
Number of real estate property purchased, in properties	36
Number of properties contributed by affiliate, in properties					63
Number of Real Estate Properties						125	1	2
Business Acquisition, Pending Purchase Price Allocation	8,000,000								5,100,000	1,100,000	1,800,000
Proceeds from sale of property held for sale	$ 553,000	$ 0		$ 600,000