Under our various plans, senior and other management employees and nonemployee directors have received nonvested stock and stock units. In conjunction with the acquisition of Time Warner, restricted stock units issued under Time Warner plans were converted to AT&T share units that will be distributed in the form of AT&T common stock and cash. The shares will vest over a period of one to four years in accordance with the terms of those plans. In addition, outstanding Time Warner stock options were converted to AT&T stock options that vested within one year. We do not intend to issue any additional grants under the Time Warner Inc. plans. Future grants to eligible employees will be issued under AT&T plans.

We grant performance stock units, which are nonvested stock units, based upon our stock price at the date of grant and award them in the form of AT&T common stock and cash at the end of a three-year period, subject to the achievement of certain performance goals. We treat the cash settled portion of these awards as a liability. We grant forfeitable restricted stock and stock units, which are valued at the market price of our common stock at the date of grant and predominantly vest over a four- or five-year period. We also grant other nonvested stock units and award them in cash at the end of a three-year period, subject to the achievement of certain market based conditions. As of December 31, 2020, we were authorized to issue up to approximately 183 million shares of common stock (in addition to shares that may be issued upon exercise of outstanding options or upon vesting of performance stock units or other nonvested stock units) to officers, employees and directors pursuant to these various plans.

We account for our share-based payment arrangements based on the fair value of the awards on their respective grant date, which may affect our ability to fully realize the value shown on our consolidated balance sheets of deferred tax assets associated with compensation expense. We record a valuation allowance when our future taxable income is not expected to be sufficient to recover the asset. Accordingly, there can be no assurance that the current stock price of our common shares will rise to levels sufficient to realize the entire tax benefit currently reflected on our consolidated balance sheets. However, to the extent we generate excess tax benefits (i.e., those additional tax benefits in excess of the deferred taxes associated with compensation expense previously recognized) the potential future impact on income would be reduced.


	2020		2019		2018
Performance stock units	$	348	$	544	$	301
Restricted stock and stock units	290		273		153
Other nonvested stock units	—		7		4
Stock options	—		(5)		5
Total	$	638	$	819	$	463
Income tax benefit	$	157	$	202	$	114


Nonvested Stock Units	Shares	Weighted-Average Grant- Date Fair Value
Nonvested at January 1, 2020	42	$	33.80
Granted	23	36.90
Vested	(18)	35.87
Forfeited	(4)	34.48
Nonvested at December 31, 2020	43	$	34.50

As of December 31, 2020, there was $709 of total unrecognized compensation cost related to nonvested share-based payment arrangements granted. That cost is expected to be recognized over a weighted-average period of 2.09 years. The total fair value of shares vested during the year was $647 for 2020, compared to $798 for 2019 and $766 for 2018.