Derivatives and Fair Value of Financial Instruments - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets:
Trading securities	$ 1,434	$ 1,336
Commodities
Assets:
Margin account	13	15
Domestic equity securities
Assets:
Trading securities	706	632
Domestic debt securities
Assets:
Trading securities	409	268
Foreign equity securities
Assets:
Trading securities	189	218
High yield securities
Assets:
Trading securities	56	19
Foreign debt securities
Assets:
Trading securities	43	16
Money market funds held in trading accounts
Assets:
Trading securities	12	146
Recurring basis | Level 1
Assets:
Total assets	1,095	1,282
Liabilities:
Total liabilities	4	4
Recurring basis | Level 1 | Commodities
Assets:
Derivatives	6	4
Liabilities:
Derivatives	4	4
Recurring basis | Level 1 | Domestic equity securities | Short term investments
Assets:
Trading securities	706	632
Recurring basis | Level 1 | Domestic equity securities | Other current assets
Assets:
Trading securities	40	32
Recurring basis | Level 1 | Domestic debt securities | Short term investments
Assets:
Trading securities	117	215
Recurring basis | Level 1 | Foreign equity securities | Short term investments
Assets:
Trading securities	189	218
Recurring basis | Level 1 | Foreign equity securities | Other current assets
Assets:
Trading securities	3	3
Recurring basis | Level 1 | High yield securities | Short term investments
Assets:
Trading securities	10	7
Recurring basis | Level 1 | Foreign debt securities | Short term investments
Assets:
Trading securities		2
Recurring basis | Level 1 | Money market funds held in trading accounts | Short term investments
Assets:
Trading securities	12	146
Recurring basis | Level 1 | Money market funds held in trading accounts | Other current assets
Assets:
Trading securities	6	5
Recurring basis | Level 1 | Other trading investments | Short term investments
Assets:
Trading securities	4	14
Recurring basis | Level 1 | Fixed income securities | Other current assets
Assets:
Trading securities	2	3
Recurring basis | Level 1 | Other | Other current assets
Assets:
Trading securities		1
Recurring basis | Level 2
Assets:
Total assets	396	111
Liabilities:
Total liabilities	3	5
Recurring basis | Level 2 | Commodities
Assets:
Derivatives		2
Recurring basis | Level 2 | Foreign currencies
Assets:
Derivatives		2
Liabilities:
Derivatives	3
Recurring basis | Level 2 | Domestic debt securities | Short term investments
Assets:
Trading securities	292	53
Recurring basis | Level 2 | High yield securities | Short term investments
Assets:
Trading securities	46	12
Recurring basis | Level 2 | Foreign debt securities | Short term investments
Assets:
Trading securities	43	14
Recurring basis | Level 2 | Collateralized loan obligations | Short term investments
Assets:
Trading securities	15	28
Recurring basis | Level 2 | Other trading investments | Short term investments
Liabilities:
Derivatives		5
Recurring basis | Level 3
Liabilities:
Contingent consideration	13	13
Total liabilities	13	13
Recurring basis | Fair Value
Assets:
Total assets	1,491	1,393
Liabilities:
Contingent consideration	13	13
Total liabilities	20	22
Recurring basis | Fair Value | Commodities
Assets:
Derivatives	6	6
Liabilities:
Derivatives	4	4
Recurring basis | Fair Value | Foreign currencies
Assets:
Derivatives		2
Liabilities:
Derivatives	3
Recurring basis | Fair Value | Domestic equity securities | Short term investments
Assets:
Trading securities	706	632
Recurring basis | Fair Value | Domestic equity securities | Other current assets
Assets:
Trading securities	40	32
Recurring basis | Fair Value | Domestic debt securities | Short term investments
Assets:
Trading securities	409	268
Recurring basis | Fair Value | Foreign equity securities | Short term investments
Assets:
Trading securities	189	218
Recurring basis | Fair Value | Foreign equity securities | Other current assets
Assets:
Trading securities	3	3
Recurring basis | Fair Value | High yield securities | Short term investments
Assets:
Trading securities	56	19
Recurring basis | Fair Value | Foreign debt securities | Short term investments
Assets:
Trading securities	43	16
Recurring basis | Fair Value | Collateralized loan obligations | Short term investments
Assets:
Trading securities	15	28
Recurring basis | Fair Value | Money market funds held in trading accounts | Short term investments
Assets:
Trading securities	12	146
Recurring basis | Fair Value | Money market funds held in trading accounts | Other current assets
Assets:
Trading securities	6	5
Recurring basis | Fair Value | Other trading investments | Short term investments
Assets:
Trading securities	4	14
Liabilities:
Derivatives		5
Recurring basis | Fair Value | Fixed income securities | Other current assets
Assets:
Trading securities	$ 2	3
Recurring basis | Fair Value | Other | Other current assets
Assets:
Trading securities		$ 1