Stock-based compensation expense was $66 million in 2018, $61 million in 2017 and $65 million in 2016. The Company recognized income tax benefits related to stock-based compensation of $24 million in 2018, $35 million in 2017 and $31 million in 2016.

The Company’s equity incentive compensation plan allows for the issuance of various forms of stock-based compensation, including stock options, restricted stock, restricted stock units and performance-based awards. At December 31, 2018 and 2017, respectively, there were 2,833,428 and 3,278,036 shares available for future grant under the Company’s equity incentive compensation plan.

Restricted stock awards are comprised of restricted stock and restricted stock units. Restricted stock awards granted since 2014 vest over three years. Restricted stock awards granted prior to 2014 vested over four years. A portion of restricted stock awards granted after 2013 require a performance condition to be met before such awards vest. Unrecognized compensation expense associated with restricted stock was $5 million as of December 31, 2018 and is expected to be recognized over a weighted-average period of approximately one year. The Company may issue restricted shares from treasury stock to the extent available or issue new shares. The number of restricted shares issued was 181,939 in 2017 and 218,341 in 2016, with a weighted-average grant date fair value of $29,557,000 in 2017 and $24,085,000 in 2016. There were no restricted shares issues in 2018. Unrecognized compensation expense associated with restricted stock units was $18 million as of December 31, 2018 and is expected to be recognized over a weighted-average period of approximately one year. The number of restricted stock units issued was 348,512 in 2018, 235,983 in 2017 and 348,297 in 2016, with a weighted-average grant date fair value of $66,050,000, $38,364,000 and $38,795,000, respectively.

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

Unvested at January 1, 2018		482,557		$	133.05		373,744		$	135.41
Granted		348,512			189.52		—			—
Vested		(265,027	)		127.39		(182,905	)		126.60
Cancelled		(9,167	)		194.45		(11,400	)		138.52
Unvested at December 31, 2018		556,875		$	170.07		179,439		$	144.18

Stock options issued generally vest over three years and are exercisable over terms not exceeding ten years and one day. Stock options issued prior to 2018 generally vested over four years. The Company used an option pricing model to estimate the grant date present value of stock options granted. The Company granted 116,852 stock options in 2018. Stock options granted in 2017 and 2016 were not significant.

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

Outstanding at January 1, 2018		665,412		$	152.23
Granted		116,852			190.78
Exercised		(535,724	)		154.91
Expired		(25,949	)		221.81
Outstanding at December 31, 2018		220,591		$	157.98		5.3	$	2,739
Exercisable at December 31, 2018		103,725		$	121.11		5.3	$	2,737

For 2018, 2017 and 2016, M&T received $60 million, $72 million and $172 million, respectively, in cash and realized tax benefits from the exercise of stock options of $3 million, $10 million and $15 million, respectively. The intrinsic value of stock options exercised during those periods was $16 million, $31 million and $42 million, respectively. As of December 31, 2018, 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 2018, 2017 and 2016 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, 2,500,000 shares of M&T common stock were authorized for issuance under a plan adopted in 2013. There were 58,167 shares issued in 2018, 66,504 shares issued in 2017 and 97,880 shares issued in 2016. For 2018, 2017 and 2016, M&T received $9,987,000, $9,730,000 and $9,528,000, respectively, in cash for shares purchased through the employee stock purchase plan. Compensation expense recognized for the stock purchase plan was not significant in 2018, 2017 or 2016.

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 18,292 and 19,633 at December 31, 2018 and 2017, 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, 2018, 269,373 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 6,271 and 7,505 at December 31, 2018 and 2017, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.