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Fair Value Measurements Fair Value Measurements (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Mar. 31, 2012
Fair Value Measurements [Abstract]      
Risk Adjusted Interest Rate 5.00% 9.50%  
Long-term Debt, Fair Value $ 427 $ 426 $ 428