Fair Value Measurements (Fair Value Measurements At Reporting Date) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets:
Deferred receivables consideration	$ 379	$ 307
Fair Value, Measurements, Recurring [Member]
Assets:
Inventories carried at market	4,547	4,886
Cash Equivalents	1,288	352
Debt Securities, Available-for-sale	13	92
Segregated investments	1,044	1,733
Deferred receivables consideration	379	307
Total Assets	7,907	7,819
Liabilities:
Inventory-related payables	597	719
Total Liabilities	1,358	1,183
Fair Value, Measurements, Recurring [Member] | Commodity Contracts [Member]
Assets:
Derivative Asset	461	386
Liabilities:
Derivative Liability	589	371
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member]
Assets:
Derivative Asset	175	63
Liabilities:
Derivative Liability	152	92
Fair Value, Measurements, Recurring [Member] | Interest Rate Contracts [Member]
Liabilities:
Derivative Liability	20	1
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Assets:
Inventories carried at market	0	0
Cash Equivalents	1,288	352
Debt Securities, Available-for-sale	12	91
Segregated investments	1,044	1,733
Deferred receivables consideration	0	0
Total Assets	2,344	2,176
Liabilities:
Inventory-related payables	0	0
Total Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Commodity Contracts [Member]
Assets:
Derivative Asset	0	0
Liabilities:
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Foreign Exchange Contract [Member]
Assets:
Derivative Asset	0	0
Liabilities:
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Interest Rate Contracts [Member]
Liabilities:
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Inventories carried at market	3,032	3,400
Debt Securities, Available-for-sale	1	1
Segregated investments	0
Deferred receivables consideration	379	307
Total Assets	3,893	4,046
Liabilities:
Inventory-related payables	579	680
Total Liabilities	1,095	1,041
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commodity Contracts [Member]
Assets:
Derivative Asset	306	275
Liabilities:
Derivative Liability	344	268
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Exchange Contract [Member]
Assets:
Derivative Asset	175	63
Liabilities:
Derivative Liability	152	92
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Contracts [Member]
Liabilities:
Derivative Liability	20	1
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Inventories carried at market	1,515	1,486
Debt Securities, Available-for-sale	0	0
Deferred receivables consideration	0	0
Total Assets	1,670	1,597
Liabilities:
Inventory-related payables	18	39
Total Liabilities	263	142
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commodity Contracts [Member]
Assets:
Derivative Asset	155	111
Liabilities:
Derivative Liability	245	103
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign Exchange Contract [Member]
Assets:
Derivative Asset	0	0
Liabilities:
Derivative Liability	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Contracts [Member]
Liabilities:
Derivative Liability	$ 0	$ 0