Quarterly report pursuant to Section 13 or 15(d)

Summary of Marketable Securities (Detail)

v3.10.0.1
Summary of Marketable Securities (Detail) - USD ($)
$ in Millions
Sep. 30, 2018
Dec. 31, 2017
Schedule of Marketable Securities [Line Items]    
Trading Securities, Short-term Investments, Amortized Cost $ 77 $ 152
Trading Securities, Gross Unrealized Gain 0 16
Trading Securities, Gross Unrealized Loss 0 0
Trading Securities 77 168
Available-for-sale Securities, Amortized Cost Basis 675 584
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0 1
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax (8) (4)
Available-for-sale Securities, Current 667 581
Total Amortized Cost 752 736
Marketable Securities, Gross Unrealized Gain 0 17
Marketable Securities, Gross Unrealized Loss (8) (4)
Total Estimated Fair Value 744 749
Corporate debt securities    
Schedule of Marketable Securities [Line Items]    
Trading Securities, Short-term Investments, Amortized Cost 75 75
Trading Securities, Gross Unrealized Gain 0 0
Trading Securities, Gross Unrealized Loss 0 0
Trading Securities 75 75
Available-for-sale Securities, Amortized Cost Basis 277 201
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0 1
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax (2) (1)
Available-for-sale Securities, Current 275 201
Carbon credit investments    
Schedule of Marketable Securities [Line Items]    
Trading Securities, Short-term Investments, Amortized Cost   77
Trading Securities, Gross Unrealized Gain   16
Trading Securities, Gross Unrealized Loss   0
Trading Securities   93
U.S. government and agency debt securities    
Schedule of Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost Basis 297 286
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0 0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax (5) (3)
Available-for-sale Securities, Current 292 283
Mortgage and asset-backed debt securities    
Schedule of Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost Basis 85 86
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0 0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax (1) 0
Available-for-sale Securities, Current 84 86
Equity securities    
Schedule of Marketable Securities [Line Items]    
Trading Securities, Short-term Investments, Amortized Cost 2  
Trading Securities, Gross Unrealized Gain 0  
Trading Securities, Gross Unrealized Loss 0  
Trading Securities 2  
Available-for-sale Securities, Amortized Cost Basis   2
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax   0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax   0
Available-for-sale Securities, Current   2
Non-U.S. government debt securities    
Schedule of Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost Basis 16 9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0 0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax 0 0
Available-for-sale Securities, Current $ 16 $ 9