Quarterly report pursuant to Section 13 or 15(d)

Summary of Marketable Securities (Detail)

v2.4.0.8
Summary of Marketable Securities (Detail) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Marketable Securities, Amortized Cost Basis $ 1,367 $ 582
Marketable Securities, Gross Unrealized Gain 2 2
Marketable Securities, Gross Unrealized Loss 2 4
Total Estimated Fair Value 1,367 580
U.S. government and agency debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Marketable Securities, Amortized Cost Basis 338 355
Marketable Securities, Gross Unrealized Gain 0 0
Marketable Securities, Gross Unrealized Loss 1 1
Total Estimated Fair Value 337 354
Mortgage and asset-backed debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Marketable Securities, Amortized Cost Basis 95 76
Marketable Securities, Gross Unrealized Gain 1 1
Marketable Securities, Gross Unrealized Loss 1 2
Total Estimated Fair Value 95 75
Corporate debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Marketable Securities, Amortized Cost Basis 817 146
Marketable Securities, Gross Unrealized Gain 1 1
Marketable Securities, Gross Unrealized Loss 0 1
Total Estimated Fair Value 818 146
Other debt and equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Marketable Securities, Amortized Cost Basis 117 5
Marketable Securities, Gross Unrealized Gain 0 0
Marketable Securities, Gross Unrealized Loss 0 0
Total Estimated Fair Value $ 117 $ 5