Stock-based compensation expense was $76 million in 2019, $66 million in 2018 and $61 million in 2017. The Company recognized income tax benefits related to stock-based compensation of $19 million in 2019, $24 million in 2018 and $35 million in 2017.

The Company’s equity incentive compensation plan allows for the issuance of various forms of stock-based compensation, including stock options, restricted stock and restricted stock units, including performance-based awards. At December 31, 2019 and 2018, respectively, there were 3,742,478 and 2,833,428 shares available for future grant under the Company’s equity incentive compensation plan.

Stock awards are comprised of restricted stock and restricted stock units. Stock awards granted since 2014 generally vest over three years. Stock awards granted prior to 2014 vested over four years. A portion of stock awards granted after 2013 require a performance condition to be met before such awards vest. The Company may issue shares from treasury stock to the extent available or issue new shares. The number of restricted shares issued was 181,939 in 2017 with a weighted-average grant date fair value of $30 million. There were no restricted shares issued in 2019 or 2018. The number of restricted stock units issued was 448,487 in 2019, 348,512 in 2018 and 235,983 in 2017, with a weighted-average grant date fair value of $74 million, $66 million and $38 million, respectively. Unrecognized compensation expense associated with restricted stock units was $22 million as of December 31, 2019 and is expected to be recognized over a weighted-average period of approximately one year.

	Restricted Stock Units Outstanding			Weighted- Average Grant Price		Restricted Stock Outstanding			Weighted- Average Grant Price

Unvested at January 1, 2019		556,875		$	170.07		179,439		$	144.18
Granted		448,487			164.63		—			—
Vested		(298,243	)		157.90		(113,894	)		133.69
Cancelled		(15,892	)		173.48		(1,954	)		161.42
Unvested at December 31, 2019		691,227		$	171.72		63,591		$	162.45

Stock options issued generally vest over three years and are exercisable over terms not exceeding ten years and one day. The Company used an option pricing model to estimate the grant date present value of stock options granted. The Company granted 164,244 and 116,852 stock options in 2019 and 2018, respectively. Stock options granted in 2017 were not significant. The fair value of options granted in each of 2019, 2018 and 2017 was not material.

				Weighted-Average
	Stock Options Outstanding			Exercise Price		Life (In Years)		Aggregate Intrinsic Value (In thousands)

Outstanding at January 1, 2019		220,591		$	157.98
Granted		164,244			164.54
Exercised		(76,181	)		122.55
Expired		(3,202	)		176.41
Outstanding at December 31, 2019		305,452		$	170.15		8.0	$	2,301
Exercisable at December 31, 2019		66,076		$	159.96		5.1	$	1,454

For 2019, 2018 and 2017, M&T received $9 million, $60 million and $72 million, respectively, in cash and realized tax benefits from the exercise of stock options of $1 million, $3 million and $10 million, respectively. The intrinsic value of stock options exercised during those periods was $3 million, $16 million and $31 million, respectively. As of December 31, 2019, the amount of unrecognized compensation cost related to non-vested stock options was not material. The total grant date fair value of stock options vested during 2019, 2018 and 2017 was not material. Upon the exercise of stock options, the Company may issue shares from treasury stock to the extent available or issue new shares.

The stock purchase plan provides eligible employees of the Company with the right to purchase shares of M&T common stock at a discount through accumulated payroll deductions. In connection with the employee stock purchase plan, shares of M&T common stock issued were 71,676 in 2019, 58,167 in 2018 and 66,504 in 2017. As of December 31, 2019, there were 2,310,751 shares available for issuance under the plan. M&T received cash for shares purchased through the employee stock purchase plan of $11 million in 2019 and $10 million in each of 2018 and 2017. Compensation expense recognized for the stock purchase plan was not significant in 2019, 2018 or 2017.

The Company provided a deferred bonus plan pursuant to which eligible employees could elect to defer all or a portion of their annual incentive compensation awards and allocate such awards to several investment options, including M&T common stock. Participants could elect the timing of distributions from the plan. Such distributions are payable in cash with the exception of balances allocated to M&T common stock which are distributable in the form of M&T common stock. Shares of M&T common stock distributable pursuant to the terms of the deferred bonus plan were 16,491 and 18,292 at December 31, 2019 and 2018, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.

The Company maintains a compensation plan for non-employee members of the Company’s boards of directors and directors advisory councils that allows such members to receive all or a portion of their compensation in shares of M&T common stock. Through December 31, 2019, 282,532 shares had been issued in connection with the directors’ stock plan.

Through acquisitions, the Company assumed obligations to issue shares of M&T common stock related to deferred directors compensation plans. Shares of common stock issuable under such plans

were 5,043 and 6,271 at December 31, 2019 and 2018, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.