Derivatives and Fair Value of Financial Instruments-Deferred Comp Securities (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Assets and liabilities measured at fair value on a recurring basis and also its level within the fair value hierarchy
Transfers that occurred into or out of level 1	$ 0
Transfers that occurred into or out of level 2	0
Transfers that occurred into or out of level 3	0
Commodities
Assets:
Margin account	16	$ 10
Domestic equity securities
Assets:
Trading securities	716	482
Foreign equity securities
Assets:
Trading securities	310	199
Domestic debt securities held in mutual funds/ETFs/U.S. Treasuries
Assets:
Trading securities	175	437
High yield securities
Assets:
Trading securities	86	115
Money market funds held in trading accounts
Assets:
Trading securities	36	13
Collateralized loan obligation
Assets:
Trading securities	29	26
Other trading securities
Assets:
Trading securities	6	5
Recurring basis \| Fair Value
Assets:
Total Assets	1,414	1,321
Liabilities:
Liabilities	5	9
Recurring basis \| Fair Value \| Commodities
Assets:
Derivatives	3	3
Margin account	16	10
Liabilities:
Derivatives	2	1
Recurring basis \| Fair Value \| Interest rate swaps
Liabilities:
Derivatives	3	4
Recurring basis \| Fair Value \| Foreign currencies
Assets:
Derivatives	4	1
Liabilities:
Derivatives		4
Recurring basis \| Fair Value \| Other current assets \| Commodities
Assets:
Derivative assets and liabilities, net basis	17	12
Recurring basis \| Fair Value \| Domestic equity securities \| Short-term investments
Assets:
Trading securities	716	482
Recurring basis \| Fair Value \| Domestic equity securities \| Other current assets
Assets:
Trading securities	38	30
Recurring basis \| Fair Value \| Foreign equity securities \| Short-term investments
Assets:
Trading securities	310	199
Recurring basis \| Fair Value \| Foreign equity securities \| Other current assets
Assets:
Trading securities	5	3
Recurring basis \| Fair Value \| Domestic debt securities held in mutual funds/ETFs/U.S. Treasuries \| Short-term investments
Assets:
Trading securities	175	437
Recurring basis \| Fair Value \| High yield securities \| Short-term investments
Assets:
Trading securities	86	115
Recurring basis \| Fair Value \| Money market funds held in trading accounts \| Short-term investments
Assets:
Trading securities	36	13
Recurring basis \| Fair Value \| Collateralized loan obligation \| Short-term investments
Assets:
Trading securities	29	26
Recurring basis \| Fair Value \| Other trading securities \| Short-term investments
Assets:
Trading securities	6	5
Recurring basis \| Fair Value \| Fixed income mutual funds \| Other current assets
Assets:
Trading securities	4	3
Recurring basis \| Fair Value \| Other \| Other current assets
Assets:
Trading securities	2	4
Recurring basis \| Level 1
Assets:
Total Assets	1,312	1,194
Liabilities:
Liabilities	2	1
Recurring basis \| Level 1 \| Commodities
Assets:
Derivatives	3	3
Liabilities:
Derivatives	2	1
Recurring basis \| Level 1 \| Domestic equity securities \| Short-term investments
Assets:
Trading securities	716	482
Recurring basis \| Level 1 \| Domestic equity securities \| Other current assets
Assets:
Trading securities	38	30
Recurring basis \| Level 1 \| Foreign equity securities \| Short-term investments
Assets:
Trading securities	310	199
Recurring basis \| Level 1 \| Foreign equity securities \| Other current assets
Assets:
Trading securities	5	3
Recurring basis \| Level 1 \| Domestic debt securities held in mutual funds/ETFs/U.S. Treasuries \| Short-term investments
Assets:
Trading securities	173	437
Recurring basis \| Level 1 \| High yield securities \| Short-term investments
Assets:
Trading securities	20	15
Recurring basis \| Level 1 \| Money market funds held in trading accounts \| Short-term investments
Assets:
Trading securities	36	13
Recurring basis \| Level 1 \| Other trading securities \| Short-term investments
Assets:
Trading securities	5	5
Recurring basis \| Level 1 \| Fixed income mutual funds \| Other current assets
Assets:
Trading securities	4	3
Recurring basis \| Level 1 \| Other \| Other current assets
Assets:
Trading securities	2	4
Recurring basis \| Level 2
Assets:
Total Assets	102	127
Liabilities:
Liabilities	3	8
Recurring basis \| Level 2 \| Interest rate swaps
Liabilities:
Derivatives	3	4
Recurring basis \| Level 2 \| Foreign currencies
Assets:
Derivatives	4	1
Liabilities:
Derivatives		4
Recurring basis \| Level 2 \| Domestic debt securities held in mutual funds/ETFs/U.S. Treasuries \| Short-term investments
Assets:
Trading securities	2
Recurring basis \| Level 2 \| High yield securities \| Short-term investments
Assets:
Trading securities	66	100
Recurring basis \| Level 2 \| Collateralized loan obligation \| Short-term investments
Assets:
Trading securities	29	$ 26
Recurring basis \| Level 2 \| Other trading securities \| Short-term investments
Assets:
Trading securities	$ 1

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