Regulatory Matters - SPPC - Regulatory Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Total regulatory assets	$ 3,963	$ 3,440
Regulatory assets, current	544	283
Regulatory assets, noncurrent	3,419	3,157
Regulatory assets not earning a return on investment	1,800	1,600
Unrealized loss on derivative contracts
Regulatory Assets [Line Items]
Total regulatory assets	$ 157	31
Deferred operating costs
Regulatory Assets [Line Items]
Regulatory asset, amortization period	9 years
Total regulatory assets	$ 103	124
SPPC
Regulatory Assets [Line Items]
Total regulatory assets	440	334
Regulatory assets, current	177	67
Regulatory assets, noncurrent	263	267
Regulatory assets not earning a return on investment	$ 158	149
SPPC | Deferred energy costs
Regulatory Assets [Line Items]
Regulatory asset, amortization period	1 year
Total regulatory assets	$ 107	22
SPPC | Merger costs from 1999 merger
Regulatory Assets [Line Items]
Regulatory asset, amortization period	25 years
Total regulatory assets	$ 66	68
SPPC | Natural disaster protection plan
Regulatory Assets [Line Items]
Regulatory asset, amortization period	1 year
Total regulatory assets	$ 62	45
SPPC | Employee benefit plans
Regulatory Assets [Line Items]
Regulatory asset, amortization period	8 years
Total regulatory assets	$ 46	81
SPPC | Unrealized loss on derivative contracts
Regulatory Assets [Line Items]
Regulatory asset, amortization period	1 year
Total regulatory assets	$ 35	2
SPPC | Deferred operating costs
Regulatory Assets [Line Items]
Regulatory asset, amortization period	8 years
Total regulatory assets	$ 31	27
SPPC | Abandoned projects
Regulatory Assets [Line Items]
Regulatory asset, amortization period	5 years
Total regulatory assets	$ 19	22
SPPC | Other
Regulatory Assets [Line Items]
Total regulatory assets	$ 74	$ 67