Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The combined weighted average of the accumulated differences between the fair values on underlying shares and exercises prices to acquire such shares as of the grant date on options that were either forfeited or lapsed.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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No definition available.

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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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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Number of share options (or share units) exercised during the current period.

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Common Equity (Details 1) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock option activity
Outstanding, Shares, Beginning Balance	8,919,669
Outstanding, Weighted-Average Exercise Price, Beginning	$ 23.86
Granted, shares	1,418,560
Granted, Weighted-Average Exercise Price		$ 3.34	$ 3.17	$ 3.36
Outstanding, Shares, Ending Balance		8,919,669
Outstanding, Weighted-Average Exercise Price, Ending		$ 23.86
Exercisable, shares		7,217,394
Exercisable, Weighted-Average Exercise Price		$ 22.19
Stock Options [Member]
Stock option activity
Outstanding, Shares, Beginning Balance		10,638,750
Outstanding, Weighted-Average Exercise Price, Beginning		$ 21.65
Granted, Weighted-Average Exercise Price		$ 34.88
Exercised, shares		(2,643,931)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price		$ 18.84
Forfeited, shares		(13,920)
Forfeited, Weighted-Average Exercise Price		$ 28.88
Outstanding, Shares, Ending Balance		8,919,669
Outstanding, Weighted-Average Exercise Price, Ending		$ 23.86
Outstanding, Weighted-Average Remaining Contractual Life (Years)		5 years 3 months
Outstanding, Aggregate Intrinsic Value		$ 115.8
Exercisable, shares		7,217,394
Exercisable, Weighted-Average Exercise Price		$ 22.19
Exercisable, Weighted-Average Remaining Contractual Life (Years)		4 years 7 months
Exercisable, Aggregate Intrinsic Value		$ 105.8