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
Mar. 31, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 1,091 $ 582
Available-for-sale Securities, Gross Unrealized Gain(1) 2 2
Available-for-sale Securities, Gross Unrealized Loss(1) 4 4
Total Estimated Fair Value 1,089 580
U.S. government and agency debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 354 355
Available-for-sale Securities, Gross Unrealized Gain(1) 1 0
Available-for-sale Securities, Gross Unrealized Loss(1) 1 1
Total Estimated Fair Value 354 354
Mortgage and asset-backed debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 78 76
Available-for-sale Securities, Gross Unrealized Gain(1) 0 1
Available-for-sale Securities, Gross Unrealized Loss(1) 1 2
Total Estimated Fair Value 77 75
Corporate debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 655 146
Available-for-sale Securities, Gross Unrealized Gain(1) 1 1
Available-for-sale Securities, Gross Unrealized Loss(1) 2 1
Total Estimated Fair Value 654 146
Other debt and equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 4 5
Available-for-sale Securities, Gross Unrealized Gain(1) 0 0
Available-for-sale Securities, Gross Unrealized Loss(1) 0 0
Total Estimated Fair Value $ 4 $ 5