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Purchase of Boardwalk Pipeline Common Units - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
6 Months Ended
Jun. 29, 2018
Jun. 30, 2018
Business Acquisition [Line Items]    
Mandatory redeemable equity liability   $ 1,500
Purchase of Boardwalk Pipeline common units   (1,715)
Increase to deferred income tax liabilities   211
Subsidiaries [Member] | Boardwalk Gp Lp [Member] | Boardwalk Pipeline [Member]    
Business Acquisition [Line Items]    
Purchase price $ 1,500  
Purchase price, per unit $ 12.06  
Additional Paid-in Capital [Member]    
Business Acquisition [Line Items]    
Purchase of Boardwalk Pipeline common units   661
Accumulated Other Comprehensive Income (Loss) [Member]    
Business Acquisition [Line Items]    
Purchase of Boardwalk Pipeline common units   $ (29)