As of December 31, 2018, the Company has an Omnibus Incentive Plan under which 1,400,000 shares are reserved for restricted stock and stock options grants for employees, as well as stock grants for directors. The plan was originally approved in 2011 and replaced all prior stock-based plans except for shares and options previously issued under those plans. As of December 31, 2018 and 2017, there were 548,653 shares and 629,615 shares, respectively, of the Company’s Common Stock available for grant under the 2011 Omnibus Incentive Plan. The Company recognizes the cost of stock-based awards in net earnings for all of its stock-based compensation plans on a straight-line basis over the service period of the awards. Included in 2018 compensation expense is executive retirement charges incurred for the vesting of certain equity awards for the retiring chief executive officer, chief financial officer and chief accounting officer. The following sections describe the three types of grants in more detail.

The Company estimates the fair value of its option awards using the Black-Scholes option-pricing formula, and records compensation expense for stock options ratably over the stock option grant’s vesting period. Stock option compensation expense recognized by the Company for the year ended December 31, 2018 related to stock options was $2.1 million compared to $0.7 million in 2017 and $0.5 million in 2016.

The following table summarizes the transactions of the Company’s stock option plans for the three-year period ended December 31, 2018:

	Number of shares			Weighted- average exercise price
Options outstanding - December 31, 2015		369,612		$	22.35
Options granted		42,302		$	33.98
Options exercised		(27,656	)	$	20.59
Options forfeited		—		n/a
Options outstanding - December 31, 2016		384,258		$	23.75
Options granted		55,223		$	36.75
Options exercised		(53,198	)	$	22.83
Options forfeited		—		n/a
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
Price range $ 18.08 — $ 19.21
(weighted-average contractual life of 2.7 years)		118,900		$	18.35
Price range $ 19.30 — $ 28.33
(weighted-average contractual life of 5.3 years)		119,139		$	27.17
Price range $ 28.34 — $ 48.20
(weighted-average contractual life of 8.2 years)		138,861		$	39.55
Options outstanding - December 31, 2018		376,900
Exercisable options —
December 31, 2016		242,522		$	21.01
December 31, 2017		239,043		$	21.59
December 31, 2018		321,122		$	27.16

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

	2018			2017
Per share fair value of options granted during the period	$	18.50		$	14.38
Risk-free interest rate		2.59	%		2.06	%
Dividend yield		1.05	%		1.22	%
Volatility factor		43.2	%		46.6	%
Weighted-average expected life in years		5.3			5.3

The expected life is based on historical exercise behavior and the projected exercise of unexercised stock options. The risk-free interest rate is based on the U.S. Treasury yield curve in effect on the date of grant for the respective expected life of the option. The expected dividend yield is based on the expected annual dividends divided by the grant date market value of the Company’s Common Stock. The expected volatility is based on the historical volatility of the Company’s Common Stock.

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

As of December 31, 2018, the unrecognized compensation cost related to stock options was approximately $0.7 million, which will be recognized over a weighted average period of 2.6 years.

Non-employee directors receive an annual award of $57,000 worth of restricted shares of the Company’s Common Stock under the shareholder-approved 2011 Omnibus Incentive Plan. The Company values stock grants for directors on the closing price of the Company’s stock on the day the grant was awarded. The Company records compensation expense for this plan ratably over the annual service period beginning May 1. Director stock compensation expense recognized by the Company for the years ended December 31, 2018 and 2017 was $0.5 million compared to $0.4 million in 2016. As of December 31, 2018, the unrecognized compensation cost related to the director stock award that is expected to be recognized over the remaining three months is estimated to be approximately $0.1 million.

The Company periodically issues nonvested shares of the Company's Common Stock to certain eligible employees. The Company values restricted stock on the closing price of the Company's stock on the day the grant was awarded. The Company records compensation expense for this plan ratably over the vesting periods. Restricted stock compensation expense recognized by the Company for the year ended December 31, 2018 was $2.1 million compared to $1.1 million in 2017 and $1.0 million in 2016.

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, 2015		120,248		$	26.99
Granted		29,268		$	33.98
Vested		(40,700	)	$	25.56
Forfeited		(3,500	)	$	29.18
Nonvested at December 31, 2016		105,316		$	29.41
Granted		50,519		$	40.69
Vested		(40,762	)	$	27.18
Forfeited		(3,600	)	$	33.37
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		(2,550	)	$	36.83
Nonvested at December 31, 2018		72,902		$	42.58

As of December 31, 2018, there was $1.8 million of unrecognized compensation cost related to nonvested restricted stock that is expected to be recognized over a weighted average period of 2.0 years.