Represents the number of non-financial separate performance metrics based on which the awards vest.

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- Definition

The number of shares awarded to an employee for each unit award earned. The cash payment is calculated by multiplying the shares awarded by the fair market value of a share determined at a pre-established valuation date.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of the awards that vest based on non-financial separate performance metrics.

+ References

No definition available.

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- Definition

Represents the percentage of the equity based awards that vest based on a percentile ranking of the Company's earnings per share growth rate compared with the earnings per share growth rate of all relevant companies in a specified utilities index.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of the equity based awards that vest based on a percentile ranking of total shareholder return compared with the total shareholder return of all relevant companies in a specified utilities index.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of cash that the participant may elect as a deferred dividend equivalent payment under the first option available under the plan.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of cash that the participant may elect as a deferred grant under the first option available under the plan.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of fully transferable shares of stock that the participant may elect as a deferred dividend equivalent payment for the first option available under the plan.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of fully transferable shares of stock that the participant may elect as a deferred grant for the first option available under the plan.

+ References

No definition available.

+ Details

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- Definition

Represents the cash required to settle the payment for grant of equity-based awards other than stock (or unit) option plans.

+ References

No definition available.

+ Details

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- Definition

The number of units granted during the period on other than stock (or unit) option plans.

+ References

No definition available.

+ Details

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- Definition

Number of performance elements criteria that affect the number of shares received after the end of the specified performance period, if performance criteria conditions are met.

+ References

No definition available.

+ Details

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- Definition

Represents the number of shares issued as a percentage of the target award.

+ References

No definition available.

+ Details

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- Definition

Percentage of awards that are no longer contingent on satisfaction of either a service condition, market condition or a performance condition on the first vesting year from the grant date, thereby giving the employee the legal right to convert the award to shares.

+ References

No definition available.

+ Details

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- Definition

Percentage of awards that are no longer contingent on satisfaction of either a service condition, market condition or a performance condition on the second vesting year from the grant date, thereby giving the employee the legal right to convert the award to shares.

+ References

No definition available.

+ Details

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- Definition

Percentage of awards that are no longer contingent on satisfaction of either a service condition, market condition or a performance condition on the third vesting year from the grant date, thereby giving the employee the legal right to convert the award to shares.

+ References

No definition available.

+ Details

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- Definition

Description of the estimated period of time over which an employee is required to provide service in exchange for the equity-based payment award, which often is the vesting period. This period may be explicit or implicit based on the terms of the award, and may be presented in a variety of ways (for example, year, month and year, day, month and year, quarter of a year).

+ References

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- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

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- Definition

The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

+ References

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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(2)(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 Statement of Financial Accounting Standard (FAS)

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-Paragraph A240

-Subparagraph c(1)

-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 Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

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

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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(2)(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 Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ 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(2)(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 Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

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

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

The number of shares newly issued during the reporting period under the plan.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 65

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

-Paragraph 2

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Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified		12 Months Ended																												0 Months Ended		12 Months Ended			1 Months Ended
	May 23, 2007 2007 grant	Dec. 31, 2011 Restricted stock unit awards	Dec. 31, 2010 Restricted stock unit awards	Dec. 31, 2009 Restricted stock unit awards	Dec. 31, 2011 Restricted stock units and stock grants stockunit	Dec. 31, 2010 Restricted stock units and stock grants stockunit	Dec. 31, 2009 Restricted stock units and stock grants stockunit	Dec. 31, 2011 Restricted stock units and stock grants 2007 grant	Dec. 31, 2010 Restricted stock units and stock grants 2007 grant	Dec. 31, 2009 Restricted stock units and stock grants 2007 grant	Dec. 31, 2011 Restricted stock units and stock grants 2008 grant	Dec. 31, 2010 Restricted stock units and stock grants 2008 grant	Dec. 31, 2009 Restricted stock units and stock grants 2008 grant	Dec. 31, 2011 Restricted stock units and stock grants 2009 grant	Dec. 31, 2010 Restricted stock units and stock grants 2009 grant	Dec. 31, 2011 Restricted stock units and stock grants 2010 grant	Dec. 31, 2011 Performance Share Awards stockunit	Dec. 31, 2010 Performance Share Awards stockunit	Dec. 31, 2009 Performance Share Awards stockunit	Dec. 21, 2011 Performance Share Awards 2007 grant criteria	Dec. 31, 2011 Performance Share Awards 2009 grant Metrics	Dec. 31, 2011 Performance Share Awards 2009 grant Maximum	Dec. 31, 2011 Performance Share Awards 2009 grant Minimum	Dec. 31, 2011 Performance Share Awards 2010 grant Metrics	Dec. 31, 2011 Performance Share Awards 2010 grant Maximum	Dec. 31, 2011 Performance Share Awards 2010 grant Minimum	Dec. 31, 2011 Performance Share Awards 2011 grant Metrics	Dec. 31, 2011 Performance Share Awards 2011 grant Maximum	Dec. 31, 2011 Performance Share Awards 2011 grant Minimum	Jan. 02, 2010 Retention Units	Jan. 02, 2009 Retention Units	Dec. 31, 2011 Retention Units	Dec. 31, 2010 Retention Units	Dec. 31, 2009 Retention Units	Jan. 31, 2009 Incentive Shares
Stock-Based Compensation
Maximum common shares to be available for grant under the 2007 Plan	8,000,000
Percentage of cash that the participant may elect as a deferral under the first option available under the plan		50.00%
Percentage of fully transferable shares of stock that the participant may elect as a deferral for the first option available under the plan		50.00%
The number of shares used to determine the cash award payable to an employee for each unit earned		1																														1
Percentage of cash that the participant may elect as a dividend equivalent deferral under the first option available under the plan		50.00%
Percentage of fully transferable shares of stock that the participant may elect as a dividend equivalent deferral for the first option available under the plan		50.00%
Vesting period (in years)		4 years	4 years	4 years																												4 years
Percentage of awards vesting on February 15, 2013		50.00%
Percentage of awards vesting on February 15, 2014		25.00%
Percentage of awards vesting on February 15, 2015		25.00%
Status of stock grants and changes during the year
Nonvested at the beginning of the period (in shares)					223,681												395,312
Granted (in shares)					293,242												175,072	178,722	240,624
Vested (in shares)					98,362												218,310
Forfeited (in shares)					2,330												4,128
Nonvested at the end of the period (in shares)					416,231	223,681											347,946	395,312
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)					$ 35.69												$ 33.44
Granted (in dollars per share)					$ 41.98	$ 37.47	$ 30.25										$ 41.71	$ 37.57	$ 30.19																$ 32.58
Vested (in dollars per share)					$ 37.84												$ 30.14
Forfeited (in dollars per share)					$ 37.93												$ 36.09
Nonvested at the end of the period (in dollars per share)					$ 39.61	$ 35.69											$ 39.64	$ 33.44
Stocks granted and the weighted average fair value
Units granted (in shares)					292,242	202,341	261,006										175,072	178,722	240,624
Grant date fair value (in dollars per share)					$ 41.98	$ 37.47	$ 30.25										$ 41.71	$ 37.57	$ 30.19																$ 32.58
Additional disclosures
Cash required to settle the payment for grant								$ 1.0	$ 0.9	$ 0.8	$ 1.6	$ 1.5	$ 1.3	$ 1.5	$ 1.4	$ 0.6														$ 1.3	$ 1.1		$ 1.3	$ 1.1
Percentage of the awards that vest based on a percentile ranking of earnings per share growth rate																					50.00%
Percentage of the awards that vest based on a percentile ranking of total shareholder return																								50.00%			50.00%
Percentage of the awards that vest based on non-financial separate performance metrics																								50.00%			50.00%
Number of performance elements criteria																				2
Number of non-financial separate performance metrics based on which awards vest																					6			6			6
Performance period (in years)																				3 years	3 years			3 years			3 years
Number of shares issued for stock grant																																			138,756
Exact number of shares issued as a percentage of the target award																						150.00%	0.00%		200.00%	0.00%		200.00%	0.00%