XML 98 R81.htm IDEA: XBRL DOCUMENT v3.8.0.1
Book Values and Fair Values of Financial Instruments (Detail) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Book Values    
Fair Value And Carrying Value By Balance Sheet Grouping [Line Items]    
Investments $ 43 $ 31
Current maturities of long-term debt and lease obligations 3 3
Long-term debt and lease obligations 3,509 2,779
Approximate fair values    
Fair Value And Carrying Value By Balance Sheet Grouping [Line Items]    
Investments 43 31
Current maturities of long-term debt and lease obligations 3 3
Long-term debt and lease obligations $ 3,595 $ 2,756