Stock-based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement, Noncash Expense [Abstract]

Stock Compensation Plans

Pursuant to stockholder approved plans, the Company has granted stock-based awards to certain employees, consultants or non-employee directors of the Company and its subsidiaries or affiliates. Following the stockholder approval of the 2022 Long-Term Incentive Plan ("2022 LTIP"), no further awards can be made under the 2013 Long-Term Incentive Plan ("2013 LTIP"). As of December 31, 2023, the Company had approximately 1 million shares available for issuance under existing awards pursuant to the 2013 LTIP and approximately 1 million and 13 million shares available for issuance under existing and future awards, respectively, pursuant to the 2022 LTIP.

Restricted Stock Units

The Company issues RSUs to certain executives and employees. Each RSU represents a contingent right to receive one share of the Company's common stock subject to satisfaction of the applicable vesting terms. The RSUs granted to certain executives and employees include (1) annual awards that contain only service-based conditions, (2) annual performance awards that vest subject to the achievement of certain stock performance-based metrics (as further described below), (3) new hire, promotional or relocation awards that generally contain only service-based vesting conditions and (4) other awards related to specific business initiatives or compensation objectives including retention and merger integration. Generally, such awards vest over periods of approximately three years.

The following is a summary of the RSU activity during the year ended December 31, 2023.


			RSUs
			(In millions)
Outstanding at the beginning of year			2
Granted			2
Vested			(1)
Forfeited			—
Outstanding at end of year			3

The Company granted approximately two million RSUs to its executives and certain other employees for the year ended December 31, 2023 and approximately one million RSUs for each of the years ended December 31, 2022 and 2021. The weighted-average grant-date fair value per share of the grants for the years ended December 31, 2023, 2022 and 2021 was $126.56, $146.52 and $155.01 per share, respectively. The weighted-average requisite service period for the RSUs granted during 2023 was approximately 2.2 years.

Of the approximately two million RSUs granted during the year ended December 31, 2023, (1) approximately 1.1 million and 0.1 million RSUs were subject to time-based vesting conditions, vesting over a three-year period and a one-year period, respectively, and (2) approximately 0.3 million RSUs were granted to the Company's executives and certain other employees and may vest on the third anniversary of the grant date based upon (a) the Company's total stockholder returns (defined as share price appreciation plus the value of dividends paid during the performance period) and (b) the Company's total stockholder return compared to that of the companies in the Standard & Poor's 500 Index. Certain RSU agreements contain provisions that result in forfeiture by the employee of any unvested shares in the event that the Company's common stock does not achieve certain performance targets. To the extent that the requisite service is rendered, compensation cost for accounting purposes is not reversed; rather, it is recognized regardless of whether or not the market performance target is achieved.

The following table summarizes the assumptions used in the Monte Carlo simulation to determine the grant-date fair value for the RSUs with market conditions granted during the years ended December 31, 2023, 2022 and 2021.


	Years Ended December 31,
	2023		2022		2021
Risk-free rate	4.5	%	1.7	%	0.2	%
Expected volatility	27	%	31	%	30	%
Expected dividend rate	4.6	%	3.0	%	3.4	%

The Company recognized aggregate stock-based compensation expense related to RSUs of $139 million, $134 million and $110 million for the years ended December 31, 2023, 2022 and 2021, respectively. The aggregate unrecognized compensation (net of estimated forfeitures) related to RSUs at December 31, 2023 is $74 million and is estimated to be recognized over a weighted-average period of less than one year.

The following table is a summary of the RSUs vested during the years ended December 31, 2023, 2022 and 2021.


Years Ended December 31,	Total Shares Vested	Fair Value on Vesting Date
	(In millions of shares)
2023	1	$	92
2022	1	187
2021	1	199

Stock-based Compensation Expense, Net

The following table discloses the components of stock-based compensation expense, net.


	Years Ended December 31,
	2023		2022		2021
Stock-based compensation expense, net:
Site rental costs of operations	$	19	$	18	$	14
Services and other costs of operations	10		10		8
Selling, general and administrative expenses	128		128		109
Total stock-based compensation expense, net	$	157	$	156	$	131