Leases - SPPC - Schedule of Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Variable	$ 611	$ 592	$ 623
Operating	161	151	170
Finance lease, amortization	23	18	16
Finance lease, interest expense	38	40	41
Total lease costs	$ 848	$ 821	$ 857
Weighted-average remaining lease term (years):
Operating leases	7 years 7 months 6 days	7 years 4 months 24 days	7 years 7 months 6 days
Finance leases	28 years 1 month 6 days	27 years 6 months	28 years 9 months 18 days
Weighted-average discount rate:
Operating leases	4.30%	4.50%	5.20%
Finance leases	8.60%	8.50%	8.60%
SPPC
Lessee, Lease, Description [Line Items]
Variable	$ 86	$ 78	$ 69
Operating	1	2	1
Finance lease, amortization	5	4	2
Finance lease, interest expense	9	9	2
Total lease costs	$ 101	$ 93	$ 74
Weighted-average remaining lease term (years):
Operating leases	27 years 4 months 24 days	27 years 2 months 12 days	26 years 3 months 18 days
Finance leases	28 years 4 months 24 days	27 years 9 months 18 days	20 years 10 months 24 days
Weighted-average discount rate:
Operating leases	5.00%	5.00%	5.00%
Finance leases	8.20%	8.10%	7.10%