Commitments and Contingencies - Schedule of Long-term Commitments (Detail) $ in Millions	Sep. 30, 2021 USD ($)
Other Commitments [Line Items]
2021	$ 543
2022	460
2023	329
2024	244
2025	218
Thereafter	2,160
Total future minimum payments	3,954
Purchased Power [Member]
Other Commitments [Line Items]
2021	7
2022	0
2023	0
2024	0
2025	0
Thereafter	0
Total future minimum payments	7
Transportation [Member]
Other Commitments [Line Items]
2021	63
2022	242
2023	221
2024	215
2025	200
Thereafter	2,068
Total future minimum payments	3,009
Capital Projects [Member]
Other Commitments [Line Items]
2021	323
2022	100
2023	64
2024	2
2025	1
Thereafter	0
Total future minimum payments	490
Fuel and Gas Supply [Member]
Other Commitments [Line Items]
2021	126
2022	82
2023	1
2024	0
2025	0
Thereafter	0
Total future minimum payments	209
Long-term Service Agreements [Member]
Other Commitments [Line Items]
2021	22
2022	30
2023	40
2024	24
2025	15
Thereafter	44
Total future minimum payments	175
Operating Leases [Member]
Other Commitments [Line Items]
2021	1
2022	3
2023	3
2024	3
2025	2
Thereafter	48
Total future minimum payments	60
Demand Side Management [Member]
Other Commitments [Line Items]
2021	1
2022	3
2023	0
2024	0
2025	0
Thereafter	0
Total future minimum payments	$ 4

Contractual obligation due after fourth year.

No definition available.

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- Definition

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

+ References

No definition available.

+ Details

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- Definition

Amount of contractual obligation to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

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- Definition

Amount of contractual obligation to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

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Amount of contractual obligation to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

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- Definition

Amount of contractual obligation to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

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- Definition

Amount of contractual obligation to be paid in remainder of current fiscal year.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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