Financial Instruments (Notional Amounts of Derivatives) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount of interest rate swaps	$ 1,000	$ 1,000
Designated as Hedging Instrument [Member] | Foreign Currency Contract [Member]
Derivative [Line Items]
Notional amount of foreign currency contracts	693	1,083
Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Notional amount of commodity contracts	597	753
Not Designated as Hedging Instrument [Member] | Foreign Currency Contract [Member]
Derivative [Line Items]
Notional amount of foreign currency contracts	9,839	6,733
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Notional amount of commodity contracts	$ 251	$ 242