Income Taxes Reconciliation of the beginning and ending amount of unrecognized tax benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits, beginning of period	$ 220	$ 220	$ 340
Current year tax positions	11	13	10
Prior year tax positions	10	30	11
Prior year tax positions	(34)	0	(62)
Settlements	(25)	0	(61)
Statute of limitations lapses	(53)	(43)	(18)
Gross unrecognized tax benefits, end of period	$ 129	$ 220	$ 220

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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The gross amount of decreases in unrecognized tax benefits resulting from tax positions taken in prior period tax returns, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from settlements with taxing authorities.

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The gross amount of increases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from lapses of the applicable statutes of limitations.

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