Income per Common Share of the Trust, Anti-dilutive (Details) (Stock Option [Member])
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Stock Option [Member]
   
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive Options Excluded from Computation of Earnings Per Share 596,000 1,247,000