Other Current Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Other Assets [Abstract]
Unrealized gains on derivative contracts	$ 636	$ 449
Deferred receivables consideration	379	307
Customer Omnibus Receivable	450	477
Financing Receivable, Net	424	413
Premiums Receivable, Net	35	129
Prepaid Expense, Current	184	232
Tax receivables	379	425
Other Receivables	323	371
Other current assets	223	372
Total other current assets	3,033	3,175		$ 3,175
Financing Receivable, Allowance for Credit Losses	3	6
Interest on financing receivables	26	25	$ 22
Reinsurance Recoverables	$ 84	$ 91