Common Equity (Details 2) (USD $)	Dec. 31, 2011
Stock options outstanding
Options Outstanding, Number, Total	10,638,750.0
Options Outstanding, Weighted-Average Exercise Price	$ 21.65
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5.4
Options Exercisable, Number, Total	7,534,980.0
Options Exercisable, Weighted-Average Exercise Price	$ 21.14
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	4.5
Range of Exercise Prices, $11.52 to $17.10 [Member]
Stock options outstanding
Options Outstanding, Number, Total	1,972,594.0
Options Outstanding, Weighted-Average Exercise Price	$ 16.07
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	2.3
Options Exercisable, Number, Total	1,972,594.0
Options Exercisable, Weighted-Average Exercise Price	$ 16.07
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	2.3
Range of Exercise Prices, $11.52 to $17.10 [Member] \| Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 17.1
Range of Exercise Prices, $11.52 to $17.10 [Member] \| Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 11.52
Range of Exercise Prices, $19.74 to $21.11 [Member]
Stock options outstanding
Options Outstanding, Number, Total	3,586,456.0
Options Outstanding, Weighted-Average Exercise Price	$ 20.62
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5.9
Options Exercisable, Number, Total	1,420,186.0
Options Exercisable, Weighted-Average Exercise Price	$ 19.88
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	4.3
Range of Exercise Prices, $19.74 to $21.11 [Member] \| Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 21.11
Range of Exercise Prices, $19.74 to $21.11 [Member] \| Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 19.74
Range of Exercise Prices, $23.88 to $29.35 [Member]
Stock options outstanding
Options Outstanding, Number, Total	5,079,700.0
Options Outstanding, Weighted-Average Exercise Price	$ 24.54
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6.2
Options Exercisable, Number, Total	4,142,200.0
Options Exercisable, Weighted-Average Exercise Price	$ 23.99
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	5.6
Range of Exercise Prices, $23.88 to $29.35 [Member] \| Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 29.35
Range of Exercise Prices, $23.88 to $29.35 [Member] \| Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 23.88

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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c), d(2)

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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- Definition

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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(b)

-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 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Share based compensation shares authorized under stock option plans exercise price range exercisable options weighted average remaining contractual term.

+ References

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- Definition

Share based compensation shares authorized under stock option plans exercise price range outstanding options weighted average remaining contractual term.

+ References

No definition available.

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