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Revenue - Revenue by Major Customers (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Revenue, Major Customer [Line Items]      
Operating revenues $ 922 $ 920 $ 840
Customer A | Revenue | Customer      
Revenue, Major Customer [Line Items]      
Operating revenues $ 560 $ 596 $ 563
Percentage of total 60.00% 65.00% 67.00%
Customer B | Revenue | Customer      
Revenue, Major Customer [Line Items]      
Operating revenues     $ 84
Percentage of total     10.00%