Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement, Noncash Expense [Abstract]

Summary of Restricted Stock Awards Activity

The following is a summary of the RSU activity during the year ended December 31, 2019.

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

Summary of the Assumptions Used in the Monte Carlo Simulation to Determine the Grant-Date Fair Value

The following table summarizes the assumptions used in the Monte Carlo simulation to determine the grant-date fair value for the awards granted during the years ended December 31, 2019, 2018 and 2017, respectively, with market conditions. 

	Years Ended December 31,
	2019		2018		2017
Risk-free rate	2.5	%	2.4	%	1.5	%
Expected volatility	18	%	18	%	18	%
Expected dividend rate	4.0	%	3.8	%	4.4	%

Summary of Restricted Stock Vested

The following table is a summary of the awards vested during the years ended December 31, 2019, 2018 and 2017.

Years Ended December 31,	Total Shares Vested	Fair Value on Vesting Date
	(In millions of shares)
2019	1	$	135
2018	1	107
2017	1	67

Stock Based Compensation Expense

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

	Years Ended December 31,
	2019		2018		2017
Stock-based compensation expense:
Site rental costs of operations	$	19	$	17	$	15
Services and other costs of operations	7		8		5
Selling, general and administrative expenses	90		83		76
Total stock-based compensation	$	116	$	108	$	96