Income per Common Share of the Trust - Dilutive (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Option [Member] | Common shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Option Exercises in Period	65,000	44,000	504,000