Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012		Mar. 31, 2011
Financial Instruments
Cash and Cash Equivalents, at Carrying Value	$ 919	$ 1,173	$ 1,293	[1]	$ 1,579
Contractual interest rate of 0.75% Convertible Senior Notes due 2016	0.75%		0.75%
Impairment charges on marketable equity securities	$ 0	$ 0
0.75% Convertible Senior Notes Due 2016
Financial Instruments
Contractual interest rate of 0.75% Convertible Senior Notes due 2016	0.75%		0.75%

[1] Derived from audited consolidated financial statements.