Consolidated Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated provision for uncollectible accounts - customers
Consolidated Valuation and Qualifying Accounts
Beginning Balance	$ 53,307	$ 68,775	$ 59,266
Charged to Income	75,859	81,719	114,249
Charged to Other Accounts	49,728	15,222	54,199
Deductions	127,607	112,409	158,939
Ending Balance	51,287	53,307	68,775
Accumulated provision for uncollectible accounts - customers \| FES
Consolidated Valuation and Qualifying Accounts
Beginning Balance	4,898	8,466	17,862
Charged to Income	2,373	4,766	7,411
Charged to Other Accounts	0	0	0
Deductions	4,921	8,334	16,807
Ending Balance	2,350	4,898	8,466
Accumulated provision for uncollectible accounts - other
Consolidated Valuation and Qualifying Accounts
Beginning Balance	884	5,231	5,197
Charged to Income	6,495	13,597	899
Charged to Other Accounts	0	11,329	4,189
Deductions	6,357	29,273	5,054
Ending Balance	1,022	884	5,231
Accumulated provision for uncollectible accounts - other \| FES
Consolidated Valuation and Qualifying Accounts
Beginning Balance	0	2,500	2,500
Charged to Income	34	0	0
Charged to Other Accounts	0	0	0
Deductions	2	2,500	0
Ending Balance	32	0	2,500
Valuation allowance on state and local DTAs
Consolidated Valuation and Qualifying Accounts
Beginning Balance	437,779	192,397	174,004
Charged to Income	142,623	245,382	18,393
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Ending Balance	580,402	437,779	192,397
Valuation allowance on state and local DTAs \| FES
Consolidated Valuation and Qualifying Accounts
Beginning Balance	197,490	45,808	32,126
Charged to Income	70,777	151,682	13,682
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Ending Balance	$ 268,267	$ 197,490	$ 45,808

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

+ Details

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- Definition

Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

+ References

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- Definition

+ References

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- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

+ References

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