Consolidated Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated provision for uncollectible accounts - customers
Consolidated Valuation and Qualifying Accounts
Beginning Balance	$ 68,775	$ 59,266	$ 51,630
Charged to Income	81,719	114,249	90,144
Charged to Other Accounts	15,222	54,199	36,373
Deductions	112,409	158,939	118,881
Ending Balance	53,307	68,775	59,266
Accumulated provision for uncollectible accounts - customers \| FES
Consolidated Valuation and Qualifying Accounts
Beginning Balance	8,466	17,862	11,073
Charged to Income	4,766	7,411	21,942
Charged to Other Accounts	0	0	0
Deductions	8,334	16,807	15,153
Ending Balance	4,898	8,466	17,862
Accumulated provision for uncollectible accounts - other
Consolidated Valuation and Qualifying Accounts
Beginning Balance	5,231	5,197	2,976
Charged to Income	13,597	899	3,469
Charged to Other Accounts	11,329	4,189	8,264
Deductions	29,273	5,054	9,512
Ending Balance	884	5,231	5,197
Accumulated provision for uncollectible accounts - other \| FES
Consolidated Valuation and Qualifying Accounts
Beginning Balance	2,500	2,500	2,523
Charged to Income	0	0	9
Charged to Other Accounts	0	0	0
Deductions	2,500	0	32
Ending Balance	0	2,500	2,500
Valuation allowance on state and local DTAs
Consolidated Valuation and Qualifying Accounts
Beginning Balance	192,397
Charged to Income	245,382
Charged to Other Accounts	0
Deductions	0
Ending Balance	437,779	192,397
Loss carryforward tax valuation reserve
Consolidated Valuation and Qualifying Accounts
Beginning Balance	192,397	174,004	125,360
Charged to Income		18,393	48,644
Charged to Other Accounts		0	0
Deductions		0	0
Ending Balance		192,397	174,004
Loss carryforward tax valuation reserve \| FES
Consolidated Valuation and Qualifying Accounts
Beginning Balance	45,808	32,126	26,875
Charged to Income	151,682	13,682	5,251
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Ending Balance	$ 197,490	$ 45,808	$ 32,126

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

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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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