Commitments and Guarantees Unrecorded Unconditional Purchase Obligations (Details) $ in Millions	Dec. 31, 2019 USD ($)
Capital Addition Purchase Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 598
Unrecorded Unconditional Purchase Obligation, Due within One Year	393
Unrecorded Unconditional Purchase Obligation, Due within Two Years	130
Unrecorded Unconditional Purchase Obligation, Due within Three Years	14
Unrecorded Unconditional Purchase Obligation, Due within Four Years	4
Unrecorded Unconditional Purchase Obligation, Due within Five Years	1
Unrecorded Unconditional Purchase Obligation, Due after Five Years	56
Long-term Contract for Purchase of Electric Power [Domain]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	3,363
Unrecorded Unconditional Purchase Obligation, Due within One Year	193
Unrecorded Unconditional Purchase Obligation, Due within Two Years	189
Unrecorded Unconditional Purchase Obligation, Due within Three Years	220
Unrecorded Unconditional Purchase Obligation, Due within Four Years	219
Unrecorded Unconditional Purchase Obligation, Due within Five Years	215
Unrecorded Unconditional Purchase Obligation, Due after Five Years	2,327
Electric Transmission [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	45
Unrecorded Unconditional Purchase Obligation, Due within One Year	0
Unrecorded Unconditional Purchase Obligation, Due within Two Years	9
Unrecorded Unconditional Purchase Obligation, Due within Three Years	9
Unrecorded Unconditional Purchase Obligation, Due within Four Years	9
Unrecorded Unconditional Purchase Obligation, Due within Five Years	9
Unrecorded Unconditional Purchase Obligation, Due after Five Years	9
Public Utility Districts [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	119
Unrecorded Unconditional Purchase Obligation, Due within One Year	16
Unrecorded Unconditional Purchase Obligation, Due within Two Years	15
Unrecorded Unconditional Purchase Obligation, Due within Three Years	13
Unrecorded Unconditional Purchase Obligation, Due within Four Years	13
Unrecorded Unconditional Purchase Obligation, Due within Five Years	12
Unrecorded Unconditional Purchase Obligation, Due after Five Years	50
Natural gas [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	827
Unrecorded Unconditional Purchase Obligation, Due within One Year	59
Unrecorded Unconditional Purchase Obligation, Due within Two Years	45
Unrecorded Unconditional Purchase Obligation, Due within Three Years	40
Unrecorded Unconditional Purchase Obligation, Due within Four Years	38
Unrecorded Unconditional Purchase Obligation, Due within Five Years	42
Unrecorded Unconditional Purchase Obligation, Due after Five Years	603
Coal and transportationSupply Agreements [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	162
Unrecorded Unconditional Purchase Obligation, Due within One Year	27
Unrecorded Unconditional Purchase Obligation, Due within Two Years	27
Unrecorded Unconditional Purchase Obligation, Due within Three Years	27
Unrecorded Unconditional Purchase Obligation, Due within Four Years	27
Unrecorded Unconditional Purchase Obligation, Due within Five Years	27
Unrecorded Unconditional Purchase Obligation, Due after Five Years	27
Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	5,114
Unrecorded Unconditional Purchase Obligation, Due within One Year	688
Unrecorded Unconditional Purchase Obligation, Due within Two Years	415
Unrecorded Unconditional Purchase Obligation, Due within Three Years	323
Unrecorded Unconditional Purchase Obligation, Due within Four Years	310
Unrecorded Unconditional Purchase Obligation, Due within Five Years	306
Unrecorded Unconditional Purchase Obligation, Due after Five Years	$ 3,072