Commitments and Guarantees Lease Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-term Purchase Commitment [Line Items]
Operating Leases, Rent Expense, Sublease Rentals	$ 4	$ 4	$ 4
Capital Leases, Future Minimum Payments Due, Next Twelve Months	6
Contractual Obligation, Due in Next Fiscal Year	11
Operating Leases, Future Minimum Payments Due, Next Twelve Months	4
Capital Leases, Future Minimum Payments Due in Two Years	6
Contractual Obligation, Due in Second Year	14
Operating Leases, Future Minimum Payments, Due in Two Years	5
Capital Leases, Future Minimum Payments Due in Three Years	6
Contractual Obligation, Due in Third Year	13
Operating Leases, Future Minimum Payments, Due in Three Years	5
Capital Leases, Future Minimum Payments Due in Four Years	6
Contractual Obligation, Due in Fourth Year	13
Operating Leases, Future Minimum Payments, Due in Four Years	6
Capital Leases, Future Minimum Payments Due in Five Years	5
Contractual Obligation, Due in Fifth Year	13
Operating Leases, Future Minimum Payments, Due in Five Years	7
Capital Leases, Future Minimum Payments Due Thereafter	67
Contractual Obligation, Due after Fifth Year	225
Operating Leases, Future Minimum Payments, Due Thereafter	97
Capital Leases, Future Minimum Payments Due	96
Contractual Obligation	289
Operating Leases, Future Minimum Payments Due	124
Capital Leases, Future Minimum Payments, Interest Included in Payments	47
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments	$ 49
Deferred Costs, Leasing, Accumulated Amortization		3
Interest Expense, Lessee, Assets under Capital Lease		$ 4