XML 61 R49.htm IDEA: XBRL DOCUMENT v3.19.1
Debt - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2019
Sep. 30, 2018
Debt Instrument [Line Items]    
Carrying value $ 17,556 $ 18,894
Senior Notes | Floating Rate Notes Due December 29, 2020    
Debt Instrument [Line Items]    
Principal amount 250  
Carrying value 249  
Repurchase amount 250  
Gain (loss) on extinguishment of debt $ (1)