Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2015	Mar. 31, 2015
Senior Subordinated Convertible Debenture Due 2025 [Member]
Debt Instrument [Line Items]
Fair value of convertible debentures based on observable market prices	$ 1,740	$ 1,788
Junior Subordinated Convertible Debentures Due 2037 Member
Debt Instrument [Line Items]
Fair value of convertible debentures based on observable market prices	$ 1,087	$ 1,124

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Convertible Security

-URI http://asc.fasb.org/extlink&oid=6509036

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant