The Company adopted a nonqualified incentive stock option plan (the “BancFirst ISOP”) in May 1986. The Company has amended the BancFirst ISOP since 1986 to increase the number of shares to be issued under the plan to 6,484,530 shares. At June 30, 2019, there were 350,000 shares available for future grants. The BancFirst ISOP will terminate on December 31, 2024, if not extended. The options vest and are exercisable beginning four years from the date of grant at the rate of 25% per year for four years. Options expire at the end of fifteen years from the date of grant. Options outstanding as of June 30, 2019 will become exercisable through the year 2026. The option price must be no less than 100% of the fair value of the stock relating to such option at the date of grant.

In June 1999, the Company adopted the BancFirst Corporation Non-Employee Directors’ Stock Option Plan (the “BancFirst Directors’ Stock Option Plan”). Each non-employee director is granted an option for 10,000 shares. The Company has amended the BancFirst Directors’ Stock Option Plan since 1999 to increase the number of shares to be issued under the plan to 530,000 shares. At June 30, 2019, there were 50,000 shares available for future grants. The BancFirst Directors’ Stock Option Plan will terminate on December 31, 2024, if not extended. The options vest and are exercisable beginning one year from the date of grant at the rate of 25% per year for four years, and expire at the end of fifteen years from the date of grant. Options outstanding as of June 30, 2019 will become exercisable through the year 2023. The option price must be no less than 100% of the fair value of the stock relating to such option at the date of grant.

The Company currently uses newly issued shares for stock option exercises, but reserves the right to use shares purchased under the Company’s Stock Repurchase Program (the “SRP”) in the future.

The following table is a summary of the activity under both the BancFirst ISOP and the BancFirst Directors’ Stock Option Plan:

						Wgtd. Avg.
				Wgtd. Avg.		Remaining	Aggregate
				Exercise		Contractual	Intrinsic
	Options			Price		Term	Value
	(Dollars in thousands, except option data)
Six Months Ended June 30, 2019
Outstanding at December 31, 2018		1,216,700		$	28.48
Options granted		40,000			55.38
Options exercised		(27,300	)		22.37
Options canceled, forfeited, or expired		(22,500	)		51.83
Outstanding at June 30, 2019		1,206,900			29.07	9.20 Yrs	$	32,090
Exercisable at June 30, 2019		648,400			22.49	7.08 Yrs	$	21,506

The following table has additional information regarding options exercised under both the BancFirst ISOP and the BancFirst Directors’ Stock Option Plan:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
	(Dollars in thousands)				(Dollars in thousands)
Total intrinsic value of options exercised	$	759	$	967	$	904	$	3,827
Cash received from options exercised		455		411		611		1,644
Tax benefit realized from options exercised		193		246		230		975

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model and is based on certain assumptions including risk-free rate of return, dividend yield, stock price volatility and the expected term. The fair value of each option is expensed over its vesting period.

The following table is a summary of the Company’s recorded stock-based compensation expense:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
	(Dollars in thousands)				(Dollars in thousands)
Stock-based compensation expense	$	367	$	322	$	541	$	628
Tax benefit		94		82		138		160
Stock-based compensation expense, net of tax	$	273	$	240	$	403	$	468

The Company will continue to amortize the unearned stock-based compensation expense over the remaining vesting period of approximately seven years. The following table shows the unearned stock-based compensation expense:

The following table shows the assumptions used for computing stock-based compensation expense under the fair value method on options granted during the periods presented:

	Six Months Ended June 30,
	2019		2018
Weighted average grant-date fair value per share of options granted	$	13.67	$	13.98
Risk-free interest rate	2.62 to 2.76%		2.55 to 2.92%
Dividend yield	2.00%		2.00%
Stock price volatility	22.93 to 22.96%		23.05 to 23.29%
Expected term	10 Yrs		10 Yrs

The risk-free interest rate is determined by reference to the spot zero-coupon rate for the U.S. Treasury security with a maturity similar to the expected term of the options. The dividend yield is the expected yield for the expected term. The stock price volatility is estimated from the recent historical volatility of the Company’s stock. The expected term is estimated from the historical option exercise experience. The Company accounts for forfeitures as they occur.

In May 1999, the Company adopted the BancFirst Corporation Directors’ Deferred Stock Compensation Plan (the “BancFirst Deferred Stock Compensation Plan”). The Company has amended the BancFirst Deferred Stock Compensation Plan since 1999 to increase the number of shares to be issued under the plan to 244,148 shares. The BancFirst Deferred Stock Compensation Plan will terminate on December 31, 2024, if not extended. Under the plan, directors and members of the community advisory boards of the Company and its subsidiaries may defer up to 100% of their board fees. They are credited for each deferral with a number of stock units based on the current market price of the Company’s stock, which accumulate in an account until such time as the director or community board member terminates serving as a board member. Shares of common stock of the Company are then distributed to the terminating director or community board member based upon the number of stock units accumulated in his or her account. There were 8,362 and 3,891 shares of common stock distributed from the BancFirst Deferred Stock Compensation Plan during the six months ended June 30, 2019 and June 30, 2018, respectively.