Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	$ 61.8	$ 61.7	$ 72.2
Charged to Costs and Expenses	26.4	33.6	41.9
Charged to Other Accounts	0.0	0.0	0.0
Deductions	34.3	33.5	52.4
Balance at End of Period	53.9	61.8	61.7
Customers
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	41.2	46.2	48.9
Charged to Costs and Expenses	12.9	17.7	23.9
Charged to Other Accounts	0.0	0.0	0.0
Deductions	17.5	22.7	26.6
Balance at End of Period	36.6	41.2	46.2
All others
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	20.6	15.5	23.3
Charged to Costs and Expenses	13.5	15.9	18.0
Charged to Other Accounts	0.0	0.0	0.0
Deductions	16.8	10.8	25.8
Balance at End of Period	17.3	20.6	15.5
Tax valuation allowance
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	24.0	32.0	29.0
Charged to Costs and Expenses	0.0	0.0	3.0
Charged to Other Accounts	4.0	0.0	0.0
Deductions	0.0	8.0	0.0
Balance at End of Period	28.0	24.0	32.0
Valuation Allowances and Reserves, Write-offs		8.0
Southern California Edison Company
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	61.1	61.7	67.6
Charged to Costs and Expenses	26.4	32.9	41.9
Charged to Other Accounts	0.0	0.0	0.0
Deductions	34.2	33.5	47.8
Balance at End of Period	53.3	61.1	61.7
Southern California Edison Company | Customers
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	40.5	46.2	48.9
Charged to Costs and Expenses	12.9	17.0	23.9
Charged to Other Accounts	0.0	0.0	0.0
Deductions	17.4	22.7	26.6
Balance at End of Period	36.0	40.5	46.2
Southern California Edison Company | All others
Movement in Valuation and Qualifying Accounts
Balance at Beginning of Period	20.6	15.5	18.7
Charged to Costs and Expenses	13.5	15.9	18.0
Charged to Other Accounts	0.0	0.0	0.0
Deductions	16.8	10.8	21.2
Balance at End of Period	$ 17.3	$ 20.6	$ 15.5