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Fair Value Measurements - Additional Information (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Fair Value [Member] | Level 2 [Member]    
Business Acquisition [Line Items]    
Long-term debt, including current maturities $ 3,541 $ 4,456
Fair Value [Member] | Market Approach [Member] | Level 2 [Member]    
Business Acquisition [Line Items]    
Long-term debt, including current maturities 3,051 $ 3,552
Liabilities Associated with Assets Held for Sale [Member]    
Business Acquisition [Line Items]    
Long-term debt $ 690