Debt Obligations Debt Footnote Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long term debt [Line Items]
Debt issuance costs-Write-off	$ (29)
Rental Expense under Operating Leases	33	$ 30	$ 32
Loss (gain) on extinguishment of debt	0	$ 3	$ (48)
Loans and Leases Receivable, Gross, Consumer, Installment and Revolving	$ 400
Line of Credit Facility, Revolving Credit Conversion to Term Loan, Description	171