Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total impairments recorded on a nonrecurring basis	$ (17)
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total impairments recorded on a nonrecurring basis	17
Royalty Based Asset [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total impairments recorded on a nonrecurring basis	$ 17