Commitments and Contingencies - Leases (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	[1]	$ 27	$ 21
Lessee, Operating Lease, Liability, to be Paid		461
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		(40)
Operating Lease, Liability		421
Operating Lease, Liability, Current		(95)		$ (90)
Operating lease liabilities		326		$ 353
Purchased Power Agreements
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		24	19
Lessee, Operating Lease, Liability, to be Paid		390
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		(28)
Operating Lease, Liability		362
Property, Plant and Equipment, Other Types
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	[2]	3	$ 2
Lessee, Operating Lease, Liability, to be Paid		71
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		(12)
Operating Lease, Liability		$ 59

[1] PPA capacity payments are included in electric fuel and purchased power on the consolidated statements of income. Expense for other operating leases is included in O&M expense and electric fuel and purchased power.

[2] Includes immaterial short-term lease expense for 2022 and 2021.