Variable Interest Entities (Textual) (Details) - Southern California Edison	1 Months Ended	3 Months Ended		12 Months Ended
	Jul. 31, 2017 USD ($)	Mar. 31, 2018 USD ($) $ / shares MW	Mar. 31, 2017 USD ($) MW	Dec. 31, 2017 USD ($) $ / shares
Variable Interest Entity
Redemption of trust securities			$ 3,000,000
Variable Interest Entity, Not Primary Beneficiary | SCE Power Purchase Contracts
Variable Interest Entity
Power generating capacity (in megawatts) | MW		3,454	4,928
Payments to unconsolidated VIEs for power purchase contracts		$ 143,000,000	$ 140,000,000
Variable Interest Entity, Not Primary Beneficiary | Trust I
Variable Interest Entity
Common stock		10,000
Variable Interest Entity, Not Primary Beneficiary | Trust I | Trust Securities
Variable Interest Entity
Security dividend rate				5.625%
Liquidation preference	$ 475,000,000	$ 475,000,000
Liquidation value (in dollars per share) | $ / shares		$ 25		$ 25
Common stock				$ 10,000
Redemption of trust securities	$ 10,000
Variable Interest Entity, Not Primary Beneficiary | Trust I | Series F Preferred Stock
Variable Interest Entity
Security dividend rate		5.625%
Liquidation preference		$ 475,000,000		$ 475,000,000
Liquidation value (in dollars per share) | $ / shares		$ 2,500		$ 2,500
Variable Interest Entity, Not Primary Beneficiary | Trust II
Variable Interest Entity
Common stock		$ 10,000
Variable Interest Entity, Not Primary Beneficiary | Trust II | Trust Securities
Variable Interest Entity
Security dividend rate				5.10%
Liquidation preference		$ 400,000,000		$ 400,000,000
Liquidation value (in dollars per share) | $ / shares		$ 25
Variable Interest Entity, Not Primary Beneficiary | Trust II | Series G Preferred Stock
Variable Interest Entity
Security dividend rate		5.10%
Liquidation preference		$ 400,000,000		$ 400,000,000
Liquidation value (in dollars per share) | $ / shares		$ 2,500
Variable Interest Entity, Not Primary Beneficiary | Trust III
Variable Interest Entity
Common stock		$ 10,000
Variable Interest Entity, Not Primary Beneficiary | Trust III | Trust Securities
Variable Interest Entity
Security dividend rate				5.75%
Liquidation preference		$ 275,000,000		$ 275,000,000
Liquidation value (in dollars per share) | $ / shares		$ 25
Variable Interest Entity, Not Primary Beneficiary | Trust III | Series H Preferred Stock
Variable Interest Entity
Security dividend rate		5.75%
Liquidation preference		$ 275,000,000		$ 275,000,000
Liquidation value (in dollars per share) | $ / shares		$ 2,500
Variable Interest Entity, Not Primary Beneficiary | Trust IV
Variable Interest Entity
Common stock		$ 10,000
Variable Interest Entity, Not Primary Beneficiary | Trust IV | Trust Securities
Variable Interest Entity
Security dividend rate				5.375%
Liquidation preference		$ 325,000,000		$ 325,000,000
Liquidation value (in dollars per share) | $ / shares		$ 25
Variable Interest Entity, Not Primary Beneficiary | Trust IV | Series J Preferred Stock
Variable Interest Entity
Security dividend rate		5.375%
Liquidation preference		$ 325,000,000		$ 325,000,000
Liquidation value (in dollars per share) | $ / shares		$ 2,500
Variable Interest Entity, Not Primary Beneficiary | Trust V
Variable Interest Entity
Common stock		$ 10,000
Variable Interest Entity, Not Primary Beneficiary | Trust V | Trust Securities
Variable Interest Entity
Security dividend rate				5.45%
Liquidation preference		$ 300,000,000		$ 300,000,000
Liquidation value (in dollars per share) | $ / shares		$ 25
Variable Interest Entity, Not Primary Beneficiary | Trust V | Series K Preferred Stock
Variable Interest Entity
Security dividend rate		5.45%
Liquidation preference		$ 300,000,000		$ 300,000,000
Liquidation value (in dollars per share) | $ / shares		$ 2,500
Variable Interest Entity, Not Primary Beneficiary | Trust VI
Variable Interest Entity
Common stock		$ 10,000
Variable Interest Entity, Not Primary Beneficiary | Trust VI | Trust Securities
Variable Interest Entity
Security dividend rate				5.00%
Liquidation preference		$ 475,000,000		$ 475,000,000
Liquidation value (in dollars per share) | $ / shares		$ 25
Variable Interest Entity, Not Primary Beneficiary | Trust VI | Series L Preferred Stock
Variable Interest Entity
Security dividend rate		5.00%
Liquidation preference		$ 475,000,000		$ 475,000,000
Liquidation value (in dollars per share) | $ / shares		$ 2,500