XML 78 R65.htm IDEA: XBRL DOCUMENT v3.10.0.1
Marketable Securities - Changes in Value of Marketable Securities Reported in Current Assets on Consolidated Balance Sheets (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Beginning Balance $ 431 $ 335
Purchase   99
Proceeds at maturity 100  
Change in fair value included in OCI (1) (3)
Change in fair value recognized in earnings 0 0
Ending Balance 330 431
U.S. Treasury Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Beginning Balance 431 335
Purchase   99
Proceeds at maturity 100  
Change in fair value included in OCI (1) (3)
Change in fair value recognized in earnings 0 0
Ending Balance $ 330 $ 431