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Pension And Other Postretirement Benefits (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2013
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Jun. 30, 2012
|
Jun. 30, 2013
|
Jun. 30, 2012
|
May 31, 2013
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Jun. 30, 2013
Pension Plan [Member]
|
Mar. 31, 2013
Pension Plan [Member]
|
Jun. 30, 2012
Pension Plan [Member]
|
Jun. 30, 2013
Pension Plan [Member]
|
Jun. 30, 2012
Pension Plan [Member]
|
Feb. 28, 2013
Pension Plan [Member]
|
Jun. 30, 2013
Other Postretirement Benefits [Member]
|
Jun. 30, 2012
Other Postretirement Benefits [Member]
|
Jun. 30, 2013
Other Postretirement Benefits [Member]
|
Jun. 30, 2012
Other Postretirement Benefits [Member]
|
|
| Defined Benefit Plan Disclosure [Line Items] | |||||||||||||||
| Pension and other postretirement benefit cost capitalized | $ 2.3 | $ 5.3 | $ 25.8 | $ 10.9 | |||||||||||
| Employer contributions | 7.2 | 20.2 | |||||||||||||
| Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements | 3.6 | 20.7 | 0 | 24.3 | 0 | 0 | 0 | 0 | 0 | ||||||
| Change in Pension Projected Benefit Obligation, net of plan assets, due to Interim Measurement | 30.7 | 18.6 | |||||||||||||
| Change in regulatory assets due to Interim Measurement | 30.8 | 36.1 | |||||||||||||
| Change in Accumulated Other Comprehensive Income due to Interim Measurement | 3.5 | 3.2 | |||||||||||||
| Change in Net Periodic Benefit Cost due to Interim Measurement | $ 4.6 | ||||||||||||||