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Supplemental Cash Flow Information (Tables)
 12 Months Ended
Dec. 31, 2018
Supplemental Cash Flow Elements [Abstract]  
Supplemental Cash Flow Information
 
Year Ended December 31,
 
2018
 
2017
 
2016
 
(in millions)
Interest paid
$
183

 
$
165

 
$
162

Income tax payments
$
108

 
$
163

 
$
120

Income tax refunds
$
7

 
$
16

 
$
8