Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Assumptions Used in Calculation of Fair Value

Below were the assumptions used in the Monte Carlo calculation:

	June 30, 2017	June 30, 2016
Expected volatility	33.6%	29.6%
Expected term (in years)	3.0	3.0
Risk-free interest rate	1.38%	0.93%

Summary of Activity Under Stock Option Plans

A summary of the activity under our stock option plans during the three and six month periods ended June 30, 2017 and changes during the six months then ended, is presented below:

	Options Outstanding		Weighted- Average Exercise Price Per Share		Weighted-Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Options outstanding at March 31, 2017	94,275		$	37.46	3.1	$	4,563,655
Options exercised	(29,317	)	$	38.46
Options forfeited	—		$	—
Options outstanding at June 30, 2017	64,958		$	37.01	3.0	$	4,651,550
Options exercisable at June 30, 2017	64,958		$	37.01	3.0	$	4,651,550
Options vested at June 30, 2017	64,958		$	37.01	3.0	$	4,651,550

	Options Outstanding		Weighted- Average Exercise Price Per Share
Options outstanding at December 31, 2016	116,575		$	37.76
Options exercised	(51,617	)	$	36.66
Options forfeited	—		$	—
Options outstanding at June 30, 2017	64,958		$	37.01

Time Based Restricted Stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Restricted Stock Activities

The following table summarizes the change in number of non-vested time-based restricted stock awards outstanding since December 31, 2016:

	Time-Based Restricted Stock Awards
Non-vested awards outstanding at December 31, 2016	239,189
Awards granted	77,005
Stock issued	(68,142	)
Awards forfeited	(4,725	)
Non-vested awards outstanding at June 30, 2017	243,327

Performance-Based Restricted Stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Restricted Stock Activities

The following table summarizes the change in number of non-vested performance-based restricted stock awards outstanding since December 31, 2016:

	Performance-Based Restricted Stock Awards
Non-vested awards outstanding at December 31, 2016	151,769
Awards granted	56,147
Stock issued	(33,887	)
Awards forfeited	(3,557	)
Non-vested awards outstanding at June 30, 2017	170,472

Deferred Stock Units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Restricted Stock Activities

The following table summarizes the change in number of deferred stock units outstanding since December 31, 2016:

	Deferred Stock Units
Awards outstanding at December 31, 2016	11,900
Awards granted	8,400
Stock issued	(11,900	)
Awards outstanding at June 30, 2017	8,400