Commitments and Contingencies - Leases (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022		Jun. 30, 2021		Jun. 30, 2022		Jun. 30, 2021		Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	$ 26	[1]	$ 20	[1]	$ 53	[2]	$ 41	[2]
Lessee, Operating Lease, Liability, to be Paid	435				435
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(36)				(36)
Operating Lease, Liability	399				399
Operating Lease, Liability, Current	(96)				(96)				$ (90)
Operating lease liabilities	303				303				$ 353
Purchased Power Agreements
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	24		17		49		36
Lessee, Operating Lease, Liability, to be Paid	366				366
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(25)				(25)
Operating Lease, Liability	341				341
Property, Plant and Equipment, Other Types
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	2	[3]	$ 3	[3]	4	[4]	$ 5	[4]
Lessee, Operating Lease, Liability, to be Paid	69				69
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(11)				(11)
Operating Lease, Liability	$ 58				$ 58

[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] 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.

[3] Includes short-term lease expense of $1 million for 2022 and 2021, respectively.

[4] Includes short-term lease expense of $1 million for 2022 and 2021, respectively.