v3.3.1.900
Investments - Summary of Cost and Carrying Value of Trading Investments (Detail) - USD ($)
$ in Millions
Dec. 31, 2015
Dec. 31, 2014
Schedule of Investments [Line Items]    
Trading investments, Cost $ 787 $ 487
Trading investments, Carrying Value 785 536
Deferred Compensation Plan Fund [Member]    
Schedule of Investments [Line Items]    
Trading investments, Cost 48 48
Trading investments, Carrying Value 65 64
Equity Securities/Multi-Asset Mutual Funds [Member]    
Schedule of Investments [Line Items]    
Trading investments, Cost 294 210
Trading investments, Carrying Value 279 239
Corporate Debt [Member]    
Schedule of Investments [Line Items]    
Trading investments, Cost 194 109
Trading investments, Carrying Value 190 110
Government Debt [Member]    
Schedule of Investments [Line Items]    
Trading investments, Cost 202 100
Trading investments, Carrying Value 202 103
Asset/Mortgage Backed Debt [Member]    
Schedule of Investments [Line Items]    
Trading investments, Cost 49 20
Trading investments, Carrying Value $ 49 $ 20