v2.4.0.6
Derivative instruments (Details Textual) (USD $)
 12 Months Ended 3 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2012
Interest expense, net [Member]
Dec. 31, 2011
Interest expense, net [Member]
Dec. 31, 2010
Interest expense, net [Member]
Dec. 31, 2012
Foreign currency option contracts [Member]
Dec. 31, 2011
Foreign currency option contracts [Member]
Dec. 31, 2010
Foreign currency option contracts [Member]
Dec. 31, 2012
Foreign currency and cross currency swap contracts [Member]
Dec. 31, 2012
Forward interest rate contracts [Member]
Dec. 31, 2011
Rate adjustment to LIBOR on Interest Rate Swap Agreements [Member]
Dec. 31, 2010
Rate adjustment to LIBOR on Interest Rate Swap Agreements [Member]
Dec. 31, 2012
Foreign currency forward contracts [Member]
Dec. 31, 2011
Foreign currency forward contracts [Member]
Dec. 31, 2010
Foreign currency forward contracts [Member]
Jun. 30, 2012
Net Cash Provided By Operating Activities [Member]
Derivative instruments (Textual) [Abstract]                                  
Notional amount             $ 200,000,000 $ 292,000,000 $ 398,000,000         $ 3,700,000,000 $ 3,500,000,000 $ 3,200,000,000  
Ineffective portions of cash flow hedging instruments (approximately), Gain (loss) (1,000,000) 1,000,000 (1,000,000)                            
Amounts expected to be reclassified from accumulated other comprehensive income into earnings over the next 12 months - gains on foreign currency and cross currency swap                   (20,000,000)              
Amounts expected to be reclassified from accumulated other comprehensive income into earnings over the next 12 months - gain (loss)                     (1,000,000)            
Derivative lower range variable interest rate                       0.30% 0.30%        
Derivative higher range variable interest rate                       2.60% 2.60%        
Interest rate swap contracts - fair value hedge - notional amounts   3,600,000,000 3,600,000,000                            
Receipt from counterparties upon termination of interest rate swap contracts                                 397,000,000
Unrealized gain (loss) on the hedged debt       (20,000,000) (182,000,000) (105,000,000)                      
Offsetting unrealized gain (loss) on related interest rate swaps       20,000,000 182,000,000 105,000,000                      
Foreign currency open contracts - not designated as hedges - notional amounts                           $ 629,000,000 $ 389,000,000 $ 670,000,000  
Length of time hedged in foreign currency contracts three years