Allowance for Uncollectible Accounts
 12 Months Ended
Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]  
Allowance for Uncollectible Accounts
Note 6: Allowance for Uncollectible Accounts
Presented in the table below are the changes in the allowances for uncollectible accounts for the years ended December 31:
 
2019
 
2018
 
2017
Balance as of January 1
$
(45
)
 
$
(42
)
 
$
(40
)
Amounts charged to expense
(28
)
 
(33
)
 
(29
)
Amounts written off
32

 
34

 
30

Recoveries of amounts written off
—

 
(4
)
 
(3
)
Balance as of December 31
$
(41
)
 
$
(45
)
 
$
(42
)