| Notional Amounts of Outstanding Derivative Positions (Detail) In Millions, unless otherwise specified | Dec. 31, 2011
 Euro
 EUR (€) | Dec. 31, 2010
 Euro
 EUR (€) | Dec. 31, 2011
 British Pound Sterling
 GBP (£) | Dec. 31, 2010
 British Pound Sterling
 GBP (£) | Dec. 31, 2011
 Canadian Dollar
 CAD | Dec. 31, 2010
 Canadian Dollar
 CAD | Dec. 31, 2011
 Fixed to Floating Interest Rate Swaps
 USD ($) | Dec. 31, 2010
 Fixed to Floating Interest Rate Swaps
 USD ($) | Dec. 31, 2011
 Floating to Fixed Interest Rate Swaps
 USD ($) | Dec. 31, 2010
 Floating to Fixed Interest Rate Swaps
 USD ($) | 
|---|---|---|---|---|---|---|---|---|---|---|
| Derivative [Line Items] | ||||||||||
| Currency Hedges | € 1,685 | € 1,732 | £ 870 | £ 871 | 318 | 289 | ||||
| Interest Rate Hedges | $ 6,424 | $ 6,000 | $ 791 | $ 53 | 
| X | ||||||||||
| 
- Details 
 | 
| X | ||||||||||
| 
- Definition Aggregate notional amount of foreign currency exchange rate derivatives. Notional amount refers to the number of currency units specified in the foreign currency derivative contract. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Aggregate notional amount of interest rate derivatives, which relates to the currency amount specified in the interest rate derivative instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 |