Leases Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Capital Leased Assets, Gross	$ 57
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	8
Capital Lease Obligations, Current	2	$ 2
Purchase Commitment, Remaining Minimum Amount Committed	47	47
Deferred Costs, Leasing, Accumulated Amortization		3
Interest Expense, Lessee, Assets under Capital Lease		4
Long-term Purchase Commitment, Amount	149
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	20
Operating Leases, Rent Expense		7
Operating Leases, Rent Expense, Contingent Rentals		14
Operating Leases, Rent Expense, Sublease Rentals		$ 4
Capital Addition Purchase Commitments [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 131