XML 42 R30.htm IDEA: XBRL DOCUMENT v3.8.0.1
Fair Value Measurements - Carrying Value and Fair Value of Other Financial Instruments (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Carrying Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, including current maturities $ 3,580 $ 4,317
Level 2 [Member] | Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, including current maturities $ 3,541 $ 4,456