Commitments and Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrecorded Unconditional Purchase Obligation [Line Items]
Capital Leased Assets, Gross	$ 57
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	8
Capital Lease Obligations, Current	2
Purchase Commitment, Remaining Minimum Amount Committed	47
Deferred Costs, Leasing, Accumulated Amortization		$ 3
Interest Expense, Lessee, Assets under Capital Lease		4
Long-term Purchase Commitment, Amount	144
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	12
Operating Leases, Rent Expense	7	9	$ 10
Operating Leases, Rent Expense, Contingent Rentals	14
Contractual Obligation	289
Operating Leases, Rent Expense, Sublease Rentals	4	4	$ 4
Capital Addition Purchase Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 131	$ 108