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Receivables (Tables)
 12 Months Ended
Dec. 31, 2019
Transfers and Servicing [Abstract]  
Schedule of Allowance for Doubtful Accounts
The following table details the changes in the allowance for doubtful accounts related to customer receivables and other receivables:
 
Customer receivables
 
Other receivables
 
2019
 
2018
 
2017
 
2019
 
2018
 
2017
Balance at beginning of year
$
4

 
$
8

 
$
13

 
$
31

 
$
34

 
$
32

Provision for doubtful accounts
3

 
2

 
1

 
13

 
7

 
9

Write off of uncollectible accounts
(2
)
 
(2
)
 
(5
)
 
(2
)
 
(2
)
 
(1
)
Recoveries of prior write-offs
—

 
—

 
—

 
(5
)
 
(3
)
 
(3
)
Other
(2
)
 
(4
)
 
(1
)
 
(4
)
 
(5
)
 
(3
)
Balance at end of year
$
3

 
$
4

 
$
8

 
$
33

 
$
31

 
$
34