A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 47

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Subparagraph 2
-Article 4

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. Such amount typically reflects adjustments similar to those made in preparing consolidated statements, including adjustments to eliminate intercompany gains and losses, and to amortize, if appropriate, any difference between cost and underlying equity in net assets of the investee at the date of investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 19
-Subparagraph c

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 11
-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 9
-Article 5

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 6
-Subparagraph b

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Interest and debt related expenses associated with nonoperating financing activities of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 34
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The cash outflow associated with other investments held by the entity for investment purposes not otherwise defined in the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 15

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount Of Decrease In Cash Taxes Due To Acceleration Of Deduction On Current Year Capital Expenditures.

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Equity method investment total income tax benefit from refined coal facility.

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Income Taxes Additional Textuals Abstract.

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Increase in the bonus depreciation allowance.

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Percentage of deduction applies to qualifying property.

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Tax credits low income housing equity method investment.

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Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2011	Apr. 30, 2010 Low-Income Housing Properties [Member]	Jun. 30, 2011 Low-Income Housing Properties [Member]	Jun. 30, 2010 Low-Income Housing Properties [Member]	Jun. 30, 2011 Low-Income Housing Properties [Member]	Jun. 30, 2010 Low-Income Housing Properties [Member]	Jun. 30, 2011 Investment In Refined Coal Facility [Member]	Jun. 30, 2011 Investment In Refined Coal Facility [Member]
Schedule of Equity Method Investments [Line Items]
Cash payments to acquire equity method investment						$ 6						$ 48
Income tax benefit, including tax credits, from equity method investment							11	11	18	11	4	7
Equity in net losses of unconsolidated entities	(9)	(8)	(13)	(8)			6	8	12	8	2	2
Interest expense	(119)	(116)	(240)	(228)			(2)	(1)	(4)	(1)
Tax credits from equity method investment							7	8	11	8
Income Taxes (Additional) (Textuals)
Effective tax rate	34.50%	44.20%	35.10%	41.20%
Increase in the bonus depreciation allowance			50 to 100 percent
Percentage of deduction that applies to qualifying property					100.00%
Expected decrease in cash taxes due to acceleration of depreciation deduction on current year capital expenditures					$ 190