Employee Stock Compensation Plans - Allocated Compensation, Assumptions and Shares Available (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation (pre-tax)	$ 33	$ 21	$ 12
Tax Benefit	(10)	(7)	(3)
Total stock-based compensation (net of tax)	23	14	9
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Dividend yield	0.00%	0.00%	0.00%
Risk-free interest rate	2.04%	2.27%	1.98%
Expected volatility	40.40%	46.80%	44.10%
Expected holding period (in years)	5.1	4.8	5
Stock Incentive Plan, 2006 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (in shares)	17
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation (pre-tax)	6	6	14
Weighted average fair value of option granted (in dollars per share)	$ 7.38	$ 5.49	$ 4.78
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation (pre-tax)	$ 27	$ 15	$ (2)

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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The amount of expense, net of income tax, 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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No definition available.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

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- Definition

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

+ References

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

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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