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Fair Value Measurements (Details) - USD ($)
$ in Millions
Jun. 30, 2022
Dec. 31, 2021
Schedule of Investments [Line Items]    
Cash $ 210 $ 121
Cash and Cash Equivalents    
Cash equivalents:    
Cost Basis 2,370 1,628
Unrealized Gains 0 0
Unrealized Losses 0 0
Fair Value 2,370 1,628
U.S. and Canadian government obligations | Cash and Cash Equivalents    
Cash equivalents:    
Cost Basis 1,942 1,452
Unrealized Gains 0 0
Unrealized Losses 0 0
Fair Value 1,942 1,452
Other debt securities | Cash and Cash Equivalents    
Cash equivalents:    
Cost Basis 218 55
Unrealized Gains 0 0
Unrealized Losses 0 0
Fair Value 218 55
Nonqualified employee benefit trusts    
Cash equivalents:    
Cost Basis 16 17
Unrealized Gains 1 3
Unrealized Losses 0 0
Fair Value $ 17 $ 20