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

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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.

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

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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.

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No definition available.

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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.

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

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No definition available.

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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.

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No definition available.

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

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No definition available.

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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.

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No definition available.

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

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No definition available.

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Represents the number of additional grants to be made during the period on other than stock (or unit) option plans if performance requirements are met.

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No definition available.

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

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No definition available.

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Represents increase in the performance factor 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).

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No definition available.

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Represents the weighted average fair value at performance factor 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).

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No definition available.

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

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No definition available.

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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.

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No definition available.

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

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No definition available.

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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.

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No definition available.

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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.

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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.

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No definition available.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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 (a)(1)

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

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Period 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, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

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 as a result of the occurrence of a terminating event.

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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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).

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

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-Name Accounting Standards Codification

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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).

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

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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 Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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

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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.

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-Name Accounting Standards Codification

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

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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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Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified		12 Months Ended																													1 Months Ended
	May 16, 2012 2012 grant	Dec. 31, 2013 Restricted stock unit awards	Dec. 31, 2013 Restricted stock units and stock grants	Dec. 31, 2012 Restricted stock units and stock grants	Dec. 31, 2011 Restricted stock units and stock grants	Dec. 31, 2011 Restricted stock units and stock grants 2007 grant	Dec. 31, 2012 Restricted stock units and stock grants 2008 grant	Dec. 31, 2011 Restricted stock units and stock grants 2008 grant	Dec. 31, 2013 Restricted stock units and stock grants 2009 grant	Dec. 31, 2012 Restricted stock units and stock grants 2009 grant	Dec. 31, 2011 Restricted stock units and stock grants 2009 grant	Dec. 31, 2013 Restricted stock units and stock grants 2010 grant	Dec. 31, 2012 Restricted stock units and stock grants 2010 grant	Dec. 31, 2011 Restricted stock units and stock grants 2010 grant	Dec. 31, 2013 Restricted stock units and stock grants 2011 grant	Dec. 31, 2012 Restricted stock units and stock grants 2011 grant	Dec. 31, 2013 Restricted stock units and stock grants 2012 grant	Dec. 31, 2013 Performance Share Awards	Dec. 31, 2012 Performance Share Awards	Dec. 31, 2011 Performance Share Awards	Dec. 31, 2013 Performance Share Awards 2007 grant item	Dec. 31, 2013 Performance Share Awards 2011 grant item	Dec. 31, 2013 Performance Share Awards 2011 grant Maximum	Dec. 31, 2013 Performance Share Awards 2011 grant Minimum	Dec. 31, 2013 Performance Share Awards 2012 grant item	Dec. 31, 2013 Performance Share Awards 2012 grant Maximum	Dec. 31, 2013 Performance Share Awards 2012 grant Minimum	Dec. 31, 2013 Performance Share Awards 2013 grant item	Dec. 31, 2013 Performance Share Awards 2013 grant Maximum	Dec. 31, 2013 Performance Share Awards 2013 grant Minimum	Dec. 31, 2012 Retention Units
Stock-Based Compensation
Common shares to be available for grant under the 2012 Long Term Incentive Plan	4,595,500
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
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		4 years
Additional shares to be granted as retention award if performance requirements are met																															33,745
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%
Stocks granted and the weighted average fair value
Units granted (in shares)			129,620	202,278	292,242													176,332	185,878	175,072
Grant date fair value (in dollars per share)			$ 55.21	$ 49.31	$ 41.98													$ 55.45	$ 47.40	$ 41.71
Nonvested shares
Balance at the beginning of the period (in shares)			480,753															347,690
Granted (in shares)			129,620															176,332													50,617
Increase in performance factor (in shares)																		40,183
Vested (in shares)			191,988															200,915
Forfeited (in shares)			20,409															18,894
Balance at the end of the period (in shares)			397,976	480,753														344,396	347,690
Weighted-Average Grant-Date Fair Value
Balance at the beginning of the period (in dollars per share)			$ 43.58															$ 44.67
Granted (in dollars per share)			$ 55.21	$ 49.31	$ 41.98													$ 55.45	$ 47.40	$ 41.71
Increase in performance factor (in dollars per share)																		$ 41.71
Vested (in dollars per share)			$ 40.33															$ 41.71
Forfeited (in dollars per share)			$ 45.70															$ 48.11
Balance at the end of the period (in dollars per share)			$ 47.74	$ 43.58														$ 51.13	$ 44.67
Cash required to settle the payment for grant						$ 1.0	$ 1.9	$ 1.6	$ 3.0	$ 1.7	$ 1.5	$ 2.3	$ 0.6	$ 0.6	$ 2.5	$ 0.7	$ 2.2
Additional disclosures
Percentage of the awards that vest based on a percentile ranking of total shareholder return																						50.00%			50.00%			50.00%
Percentage of the awards that vest based on non-financial separate performance metrics																						50.00%			50.00%			50.00%
Number of performance element criteria																					2
Number of non-financial separate performance metrics based on which awards vest																						6			6			6
Performance period																					3 years	3 years			3 years			3 years
Exact number of shares issued as a percentage of the target award																							200.00%	0.00%		200.00%	0.00%		200.00%	0.00%
Percentage of fully transferable shares of stock that the participant may elect as a deferral for the second 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 second option available under the plan		50.00%