Dispositions and Impairments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Asset Impairment and Other Related Charges	$ 726.4	$ 623.7
Other Assets [Member] \| Corporate and Other [Member]
Asset Impairment and Other Related Charges	$ 21.0
Merchant Coal-Fired Generation Assets [Member] \| Generation And Marketing [Member]
Asset Impairment and Other Related Charges		4.0
Zimmer Plant Assets [Member] \| Generation And Marketing [Member]
Asset Impairment and Other Related Charges		7.0
Gavin, Waterford, Darby and Lawrenceburg Plants [Member] \| Generation And Marketing [Member]
Cash Proceeds from Sale of Assets, Investing Activities		2,200.0
Cash Proceeds from Disposition of Plants, Net		1,200.0
Pre-tax Gain on Sale of Plants		$ 227.0

Cash Proceeds from Disposition of Business, Net

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2443-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2941-110230

+ Details

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Period Type:	duration

- Definition

Aggregate cash proceeds received from a combination of transactions that are classified as investing activities in which assets, which may include one or more investments, are sold to third-party buyers. This element can be used by entities to aggregate proceeds from all asset sales that are classified as investing activities.

+ References

No definition available.

+ Details

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- Definition

Amount of operating expense for routine operations of regulated operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(b))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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- Details

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- Details

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- Details

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- Details

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