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Stock-based Compensation (Tables)
 12 Months Ended
Dec. 31, 2016
Share-based Compensation [Abstract]  
Summary of Restricted Stock Awards Activity
The following is a summary of the RSA and RSU activity during the year ended December 31, 2016.
 
RSAs
 
RSUs
 
(In thousands)
 
(In thousands)
Outstanding at the beginning of year
663

 
1,777

Granted
—

 
1,285

Vested
(500
)
 
(328
)
Forfeited
(163
)
 
(57
)
Outstanding at end of year
—

 
2,677
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, 2016, 2015, and 2014, respectively, with market conditions. 
 
Years Ended December 31,
 
2016
 
2015
 
2014
Risk-free rate
0.9
%
 
1.0
%
 
0.7
%
Expected volatility
19
%
 
19
%
 
22
%
Expected dividend rate
4.24
%
 
4.21
%
 
1.93
%
Summary of Restricted Stock Vested
The following table is a summary of the awards vested during the three years ended December 31, 2016.
Years Ended December 31,
 
Total Shares
Vested
 
Fair Value on
Vesting Date
 
 
(In thousands
of shares)
 
 
2016
 
828

 
$
71,325

2015
 
946

 
83,244

2014
 
842

 
62,686
Stock Based Compensation Expense
The following table discloses the components of stock-based compensation expense.
 
Years Ended December 31,
 
2016
 
2015
 
2014
Stock-based compensation expense:
 
 
 
 
 
Site rental costs of operations
$
14,371

 
$
8,969

 
$
6,565

Network services and other costs of operations
7,717

 
5,370

 
4,889

General and administrative expenses
74,450

 
52,809

 
44,977

Total stock-based compensation
$
96,538

 
$
67,148

 
$
56,431