Fair Value Measurements 2 (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Mar. 31, 2011
Liabilities:
Total debt(1)	$ 1,301	$ 1,551
Carrying Value [Member]
Liabilities:
Total debt(1)	1,301	1,551
Facilities abandonment reserve (2)	42	52
Estimated Fair Value [Member]
Liabilities:
Total debt(1)	1,408	1,619
Facilities abandonment reserve (2)	$ 48	$ 59