Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Mar. 31, 2015	[1]	Jun. 30, 2014	Mar. 31, 2014
Financial Instruments
Cash and Cash Equivalents, at Carrying Value	$ 1,810	$ 2,068		$ 1,554	$ 1,782

[1] Derived from audited consolidated financial statements.