Stock Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Transactions of Stock Option Plans

The following table summarizes the transactions of the Company’s stock option plans for the three-year period ended December 31, 2020:

	Number of shares			Weighted- average exercise price
Options outstanding - December 31, 2017		386,283		$	25.74
Options granted		43,778		$	48.20
Options modified		80,642		$	52.44
Options exercised		(53,161	)	$	21.47
Options canceled		(80,642	)	$	37.04
Options forfeited		—		n/a
Options outstanding - December 31, 2018		376,900		$	28.95
Options granted		34,926		$	59.44
Options exercised		(66,969	)	$	29.29
Options forfeited		(7,525	)	$	38.81
Options outstanding - December 31, 2019		337,332		$	31.82
Options granted		41,807		$	62.76
Options exercised		(55,716	)	$	18.99
Options forfeited		(7,229	)	$	50.19
Options outstanding - December 31, 2020		316,194		$	37.75
Price range $ 18.08 — $ 27.18
(weighted-average contractual life of 2.1 years)		106,390		$	22.53
Price range $ 28.33 — $ 42.50
(weighted-average contractual life of 5 years)		102,484		$	33.30
Price range $ 48.20 — $ 72.30	.
(weighted-average contractual life of 8.2 years)		107,320		$	57.09
Options outstanding - December 31, 2020		316,194
Exercisable options —
December 31, 2018		321,122		$	27.16
December 31, 2019		271,252		$	27.17
December 31, 2020		235,829		$	30.82

Assumptions Used for Valuing Options Granted

The following assumptions were used for valuing options granted in the years ended December 31:

	2020			2019
Per share fair value of options granted during the period	$	17.49		$	18.20
Risk-free interest rate		0.64	%		2.52	%
Dividend yield		1.05	%		0.97	%
Volatility factor		30.0	%		32.4	%
Weighted-average expected life in years		7.0			5.3

Summary of Aggregate Intrinsic Value Related to Options

The following table summarizes the aggregate intrinsic value related to options exercised, outstanding and exercisable as of and for the years ended December 31:

	2020		2019
	(In thousands)
Exercised	$	3,054	$	1,870
Outstanding	$	17,805	$	11,170
Exercisable	$	14,913	$	10,243

Schedule of Fair Value of Nonvested Shares

The fair value of nonvested shares is determined based on the market price of the shares on the grant date.

	Shares			Fair value per share
Nonvested at December 31, 2017		111,473		$	35.21
Granted		32,268		$	49.10
Modified		30,488		$	52.47
Vested		(68,289	)	$	40.16
Canceled		(30,488	)	$	38.62
Forfeited		(2,650	)	$	36.83
Nonvested at December 31, 2018		72,802		$	42.58
Granted		16,034		$	59.42
Vested		(19,227	)	$	30.08
Forfeited		(5,129	)	$	41.31
Nonvested at December 31, 2019		64,480		$	48.21
Granted		20,758		$	64.19
Vested		(25,044	)	$	39.87
Forfeited		(2,645	)	$	54.35
Nonvested at December 31, 2020		57,549		$	57.33