Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended							12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012 Designated as Hedging Instrument [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2012 Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member] Matured [Member]	Mar. 31, 2013 Not Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2012 Not Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Scenario, Forecast [Member]
Derivative [Line Items]
Notional Amount of Foreign Currency Derivatives			$ 503	$ 528		$ 172	$ 177	$ 151
Maturity period, years		8 years							1 year
Derivative, Maturity Date	Jun. 30, 2013
Notional Amount of Foreign Currency Cash Flow Hedge Derivatives					$ 25