Pension and Other Postretirement Benefits (Details Textuals) (USD $) In Millions, unless otherwise specified	12 Months Ended	10 Months Ended		12 Months Ended	0 Months Ended	12 Months Ended	10 Months Ended
Dec. 31, 2011 Pensions	Dec. 31, 2010 Pensions	Dec. 31, 2009 Pensions	Dec. 31, 2011 Pensions Allegheny	Feb. 24, 2011 Pensions Allegheny	Dec. 31, 2011 Pensions Pre Tax [Member]	Jan. 05, 2012 Pensions Pre Tax [Member] Additional Contribution	Dec. 31, 2011 OPEB	Dec. 31, 2010 OPEB	Dec. 31, 2009 OPEB	Dec. 31, 2011 OPEB Allegheny	Feb. 24, 2011 OPEB Allegheny
Defined Benefit Plan Disclosure [Line Items]
Pre-tax contributions to qualified plans	$ 384	$ 11				$ 372	$ 600	$ 19	$ 59
Discount rate used to measure funded status	5.00%	5.50%		5.50%				4.75%	5.00%		5.25%
Fair value of plan assets	5,867	4,544	4,399		954			528	498	467		75
Actuarially determined benefit obligations	7,977	5,858	5,392		1,341			1,037	861	823		272
Expected returns on plan assets used to calculate net periodic costs	8.25%	8.50%	9.00%	8.25%				8.50%	8.50%	9.00%	5.00%
Estimated 2012 amortization of prior service costs (credits) from AOCI	$ 12							$ (203)

The aggregate amount in accumulated other comprehensive income expected to be recognized as a component of net periodic benefit cost over the fiscal year that follows the most recent annual statement of financial position presented, including the net gain (loss), net prior service cost or credit, and net transition asset or obligation.

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An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

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- Definition

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Projected Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6522206

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Postretirement Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503904

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 6

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph E1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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