Income Taxes (Details) (USD $) In Millions	9 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Net deferred income tax classification
Deferred tax assets	$ 285	$ 156
Changes to unrecognized tax benefits
Amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate	6
Unrecognized tax benefits at beginning of period	176
Unrecognized tax benefits at end of period	176
Open tax years by jurisdiction	Our federal tax years are open for examination from 2007 forward, and our open state tax years in our major jurisdictions are generally from 2003 forward.
Interest and penalties accrued	$ 19	$ 45

- Definition

The current portion of the aggregate tax effects as of the balance sheet date of all future tax deductions arising from temporary differences between tax basis and generally accepted accounting principles basis recognition of assets, liabilities, revenues and expenses, which can only be deducted for tax purposes when permitted under enacted tax laws; after deducting the allocated valuation allowance, if any, to reduce such amount to net realizable value. Deferred tax liabilities and assets are classified as current or noncurrent based on the classification of the related asset or liability for financial reporting. A deferred tax liability or asset that is not related to an asset or liability for financial reporting, including deferred tax assets related to carryforwards, are classified according to the expected reversal date of the temporary difference. An unrecognized tax benefit that is directly related to a position taken in a tax year that results in a net operating loss carryforward is presented as a reduction of the related deferred tax asset.

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