Earnings Per Common Share (Details) (USD $) In Millions, except Per Share data	3 Months Ended
Jun. 30, 2011	Jun. 30, 2010
Earnings Per Share Basic By Common Class of Stock [Line Items]
Net Income	$ 286	$ 298
Weighted average common shares outstanding:
Basic	249	266
Effect of dilutive securities:
Diluted	254	272
Earnings per common share:
Diluted	$ 1.13	$ 1.10
Basic	$ 1.15	$ 1.12
Earnings Per Common Share (Textuals)
Potentially dilutive shares excluded from diluted earnings per share	4	6
Options [Member]
Effect of dilutive securities:
Options to purchase common stock	2	4
Restricted Stock Units (RSUs) [Member]
Effect of dilutive securities:
Options to purchase common stock	3	2

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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