Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2016

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

Summary of Activity Under Stock Option Plans

A summary of the activity under our stock option plans as of September 30, 2016 and changes during the three and nine 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 June 30, 2016	156,057	$	41.57	3.1	$	3,085,731
Options exercised	—	$	—
Options forfeited	—	$	—
Options outstanding at September 30, 2016	156,057	$	41.57	2.9	$	3,082,880
Options exercisable at September 30, 2016	156,057	$	41.57	2.9	$	3,082,880
Options vested at September 30, 2016	156,057	$	41.57	2.9	$	3,082,880

	Options Outstanding		Weighted- Average Exercise Price Per Share
Options outstanding at December 31, 2015	212,038		$	40.47
Options exercised	(55,631	)	$	36.99
Options forfeited	(350	)	$	44.32
Options outstanding at September 30, 2016	156,057		$	41.57

Assumptions Used in Calculation of Fair Value

Below were the assumptions used in the Monte Carlo calculation:

	September 30, 2016	September 30, 2015
Expected volatility	29.6%	28.2%
Expected term (in years)	3.0	3.0
Risk-free interest rate	0.93%	0.96%

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, 2015:

	Time-Based Restricted Stock Awards
Non-vested awards outstanding at December 31, 2015	208,318
Awards granted	117,960
Stock issued	(51,525	)
Awards forfeited	(19,027	)
Non-vested awards outstanding at September 30, 2016	255,726

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, 2015:

	Performance-Based Restricted Stock Awards
Non-vested awards outstanding at December 31, 2015	107,229
Awards granted	84,443
Stock issued	(25,397	)
Awards forfeited	(10,731	)
Non-vested awards outstanding at September 30, 2016	155,544

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, 2015:

	Deferred Stock Units
Awards outstanding at December 31, 2015	23,950
Awards granted	11,900
Stock issued	(22,750	)
Awards outstanding at September 30, 2016	13,100