Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Impairment of intangible assets	$ 6		$ 8
Total impairments recorded on a nonrecurring basis	6	0	8	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Acquired finite lived intangible assets fair value disclosure	15		15
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Acquired finite lived intangible assets fair value disclosure	$ 15		$ 15