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Debt and Banking Arrangements Long-Term Debt Issuances and Retirements (Details 1) - USD ($)
$ in Millions
3 Months Ended
Jun. 15, 2018
Mar. 28, 2018
Mar. 31, 2018
Mar. 15, 2018
Mar. 05, 2018
Transcontinental Gas Pipe Line Company, LLC [Member]          
Debt Instrument [Line Items]          
Proceeds from Issuance of Other Long-term Debt     $ 19    
4.875% Senior Unsecured Notes due 2024 [Member] | Williams Partners L.P. [Member]          
Debt Instrument [Line Items]          
Long-term debt interest rate   4.875%      
Long-term debt retired   $ 750      
4.85%SeniorUnsecuredNotesDue2048 [Member] | Williams Partners L.P. [Member]          
Debt Instrument [Line Items]          
Long-term debt face amount         $ 800
Long-term debt interest rate         4.85%
4%SeniorUnsecuredNotesDue2028 [Member] | Transcontinental Gas Pipe Line Company, LLC [Member]          
Debt Instrument [Line Items]          
Long-term debt face amount       $ 400  
Long-term debt interest rate       4.00%  
Additional interest rate accrued for default of registration rights agreements first period       0.25%  
Additional interest rate accrued for default of registration rights agreements each subsequent period       0.25%  
Maximum additional interest rate accrued for default of registration rights agreements all periods       0.50%  
4.6%SeniorUnsecuredNotesDue2048 [Member] | Transcontinental Gas Pipe Line Company, LLC [Member]          
Debt Instrument [Line Items]          
Long-term debt face amount       $ 600  
Long-term debt interest rate       4.60%  
Additional interest rate accrued for default of registration rights agreements first period       0.25%  
Additional interest rate accrued for default of registration rights agreements each subsequent period       0.25%  
Maximum additional interest rate accrued for default of registration rights agreements all periods       0.50%  
6.05% Senior Unsecured Notes due 2018 [Member] | Transcontinental Gas Pipe Line Company, LLC [Member] | Subsequent Event [Member]          
Debt Instrument [Line Items]          
Long-term debt interest rate 6.05%        
Long-term debt retired $ 250