Supplementary Financial Information - Restricted Cash Balance Sheet Location (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Total Restricted cash	$ 43	$ 55
Other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Total Restricted cash	0	0
Other long-term assets
Restricted Cash and Cash Equivalents Items [Line Items]
Total Restricted cash	$ 43	$ 55