Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data	Jun. 30, 2011	Mar. 31, 2011
Stockholders' equity:
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	1.0	1.0
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	600.0	600.0
Common stock, issued	249.1	249.1
Treasury stock, shares	73.6	71.9

Face amount or stated value of common stock per share; generally not indicative of the fair market value per share.

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-Name Statement of Financial Accounting Standard (FAS)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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-Paragraph 30
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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Face amount or stated value per share of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer); generally not indicative of the fair market value per share.

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-Name Accounting Principles Board Opinion (APB)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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