The Company’s incentive compensation plans allow the Company to grant awards to employees in the form of stock options, stock awards, restricted stock units, stock appreciation rights, performance stock units, dividend equivalents and other awards. Compensation related to these awards is determined based on the grant-date fair value and is amortized to expense over the vesting period. The Company recognizes compensation expense based on the earlier of the vesting date or the date when the employee becomes eligible to retire without forfeiture of the award. If awards can be settled in cash, these awards are recorded as liabilities and recorded at fair value at each reporting date.

The following table discloses the amount of stock-based compensation expense:


	Year Ended December 31,
	2020		2019		2018
Restricted stock units	$	3,729	$	2,836	$	3,196
Performance stock units	2,324		1,526		672
Total stock-based compensation	$	6,053	$	4,362	$	3,868

The 2010 and 2014 Incentive Compensation Plans provide for granting options to key employees to purchase common shares at prices not less than market at the date of grant. Options under these plans may have terms of up to ten years becoming exercisable in whole or in consecutive installments, cumulative or otherwise. The plans allow the granting of nonqualified stock options which are not intended to qualify for the tax treatment applicable to incentive stock options under provisions of the Internal Revenue Code.

No stock options have been granted to executives participating in the Long-Term Incentive Plan since February 2014. Outstanding options do not contain any performance-based criteria. The Company recognizes compensation expense based on the earlier of the vesting date or the date when the employee becomes eligible to retire.


	Number of Shares	Weighted Average Exercise Price (per share)		Aggregate Intrinsic Value (thousands)
Outstanding at December 31, 2019	238,748	$	23.30

Exercised	(117,324)	22.48
Expired	(1,508)	23.96

Outstanding and Exercisable at December 31, 2020	119,916	$	24.08	$	1,969

Segregated disclosure of options outstanding at December 31, 2020 was as follows:


	Range of Exercise Prices
	Less than or equal to $15.63		Greater than $15.63
Options outstanding	5,965		113,951
Weighted average exercise price	$	15.63	$	24.53
Remaining contractual life	1.1		2.8
Options exercisable	5,965		113,951
Weighted average exercise price	$	15.63	$	24.53

Under the 2001 and 2014 Incentive Compensation Plans, restricted stock units may be granted to officers and certain other employees as awards for exceptional performance, as a hiring or retention incentive or as part of the Long-Term Incentive Plan. The restricted stock units granted in 2018, 2019 and 2020 have vesting periods of three to four years. Compensation expense related to the restricted stock units granted is determined based on the fair value of the Company’s stock on the date of grant. The Company recognizes compensation expense based on the earlier of the vesting date or the date when the employee becomes eligible to retire. Employees must remain employed for at least six months after the grant date to vest in the restricted stock units, even if retirement eligible.

The following table provides details of the Company's restricted stock units for 2020:


	Number of Restricted Units	Weighted Average Grant-Date Fair Value (per share)		Aggregate Intrinsic Value (thousands)
Nonvested at December 31, 2019	230,962	$	33.49
Granted	158,256	28.58
Vested	(88,672)	35.04
Canceled	(49,720)	30.02
Accrued dividend equivalents	4,376	30.62
Nonvested at December 31, 2020	255,202	$	30.86
Vested but not released	1,508	18.04
Outstanding at December 31, 2020	256,710	$	30.78	$	7,902

Weighted-average remaining contractual term of shares outstanding (months)	20



	Year Ended December 31,
	2020		2019		2018
Weighted average grant-date fair value of restricted shares granted (per share)	$	28.58	$	32.52	$	34.53
Weighted average grant-date fair value of shares vested (thousands)	$	3,107	$	3,336	$	3,000

The number of vested restricted stock units at December 31, 2020 and 2019 was 1,508 and 1,483, respectively. At December 31, 2020, the Company has $1,896 of unvested compensation cost related to restricted stock units and this cost will be recognized as expense over a weighted average period of 27 months.

Under the 2014 Incentive Compensation Plan, performance stock units may be granted as part of the Long-Term Incentive Plan. Compensation expense related to the performance stock units is determined based on the fair value of the Company’s stock on the date of grant combined with performance metrics. The Company recognizes compensation expense based on the earlier of the vesting date or the date when the employee becomes eligible to retire, and in accordance with the achievement of the underlying performance condition.


	Number of Performance Units	Weighted Average Grant- Date Fair Value (per share)		Aggregate Intrinsic Value (thousands)
Nonvested at December 31, 2019	59,335	$	33.79
Earned	92,816	27.35
Vested	(51,147)	31.50
Canceled	(20,064)	29.33
Accrued dividend equivalents	1,014	33.85
Nonvested at December 31, 2020	81,954	$	29.02
Vested but not released	49,376	31.39
Outstanding at December 31, 2020	131,330	$	29.91	$	3,928

Weighted-average remaining contractual term of performance stock units outstanding (months)	11



	Year Ended December 31,
	2020		2019		2018
Weighted average grant-date fair value of performance stock units granted (per share)	$	27.35	$	33.27	$	36.08
Weighted average grant-date fair value of performance stock units vested (thousands)	$	1,611	$	1,073	$	1,821

At December 31, 2020, the Company had $412 of unvested compensation cost related to performance stock units and this cost will be recognized as expense over a weighted average period of 19 months.

The Company’s nonvested restricted stock units and performance stock units are not participating securities. These units will be converted into shares of Company common stock in accordance with the distribution date indicated in the agreements. Restricted stock units earn dividend equivalents from the time of the award until distribution is made in common shares. Performance stock units earn dividend equivalents from the time the units have been earned based upon Company performance metrics until distribution is made in common shares. Dividend equivalents are only earned subject to vesting of the underlying restricted stock units or performance stock units. Accordingly, such units do not represent participating securities.