Real Estate Activity During The Nine Months Ended September 30, 2011 (Estimated Amortization Of The Acquired Above Market Leases (Net Of Acquired Below Market Leases) And The Acquired In-Place Lease Intangibles) (Details) (Bay Colony Corporate Center [Member], USD $) In Thousands	9 Months Ended
	Sep. 30, 2011
Acquired In-Place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Period from October 1, 2011 through December 31, 2011	$ 1,574
2012	5,192
2013	3,423
2014	2,543
2015	1,867
Acquired Net Above Market Lease Intangibles [Member]
Real Estate Properties [Line Items]
Period from October 1, 2011 through December 31, 2011	158
2012	520
2013	349
2014	221
2015	$ 300