Fair Value Measurements - Financial Instruments at Fair Value, Excluding Derivative Financial Instruments and Contingent Consideration (Detail) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Fair Value    
Financial assets:    
Environmental receivables and misc. deposits $ 18 $ 17
Total financial assets 18 17
Financial liabilities:    
Long-term debt [1] 17,893 13,893
Deferred credits and other liabilities 118 122
Total financial liabilities 18,011 14,015
Carrying Value    
Financial assets:    
Environmental receivables and misc. deposits 18 17
Total financial assets 18 17
Financial liabilities:    
Long-term debt [1] 17,010 12,642
Deferred credits and other liabilities 108 109
Total financial liabilities $ 17,118 $ 12,751
[1] Excludes capital leases and debt issuance costs; includes amount classified as debt due within one year.