Stock-Based Compensation (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Stock-Based Compensation
Stock options granted (in shares)	7
Stock options granted, weighted average fair value (in dollars per share)	$ 11.14
Stock options granted, weighted average exercise price (in dollars per share)	$ 45.07		$ 45.07
Stock options, outstanding at the end of the period (in shares)	49		49
Stock options outstanding at the end of the period, weighted average exercise price (in dollars per share)	$ 35.54		$ 35.54
Stock options outstanding at the end of the period, weighted average contractual term (in years)	4.33		4.33
Employee stock options
Stock-Based Compensation
Compensation expense related to stock options	$ 20	$ 24	$ 51	$ 55
Restricted stock awards
Stock-Based Compensation
Compensation expense related to stock options	$ 8	$ 5	$ 13	$ 10

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Net number of share options (or share units) granted during the period.

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The weighted average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on stock options awarded under the plan during the reporting period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The weighted average period between the balance sheet date and expiration for all awards outstanding under the plan, which may be expressed in a decimal value for number of years.

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