Stock-based Compensation - (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of non-vested restricted common shares

The following is summary of the status of the Trust’s non-vested restricted common shares during 2016, 2015, and 2014:

	Common Shares		Weighted Average Grant Date Fair Value
Non-vested at December 31, 2013	250,000		$	11.50
Granted	152,987		13.79
Vested	(83,333	)	11.50
Non-vested at December 31, 2014	319,654		12.60
Granted	162,522		15.95
Vested	(170,337	)	12.93
Non-vested at December 31, 2015	311,839		14.17
Granted	155,306		17.96
Vested	(170,034	)	14.16
Forfeited	(326	)	15.36
Non-vested at December 31, 2016	296,785		$	16.16

Schedule of weighted average grant date fair value assumptions

The Company utilized a Monte Carlo simulation to calculate the weighted average grant date fair values in 2016, 2015, and 2014 of $28.50, $20.06, and $19.25 per unit, respectively, using the following assumptions:

	2016			2015			2014
Volatility	20.3		%	20.7		%	18.8% - 34.2%
Dividend assumption	reinvested			reinvested			reinvested
Expected term in years	2.8 years			2.8 years			2.8 years
Risk-free rate	1.07		%	1.14		%	0.65		%
Stock price (per share)	$	17.67		$	15.87		$	13.47

Summary of the activity in the restricted share units

The following is a summary of the activity in the Trust’s restricted share units during 2016, 2015, and 2014: 

	Executive Awards			Trustee Awards
	Restricted Share Units	Weighted Average Grant Date Fair Value		Restricted Share Units		Weighted Average Grant Date Fair Value
Non-vested at December 31, 2013	—	$	—	—		$	—
Granted	55,680	16.94		—		—
Non-vested at December 31, 2014	55,680	16.94		—		—
Granted	75,250	19.22		40,957		15.87
Non-vested at December 31, 2015	130,930	18.48		40,957		15.87
Granted	104,553	26.33		36,784		17.67
Vested	—	—		(20,481	)	15.87
Non-vested at December 31, 2016	235,483	$	21.84	57,260		$	17.03