Fair Value Measurements - Recurring (Changes in Level 3 Measurements) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Commodity Derivative Contracts (net)
Derivative assets and liabilities classified by the Partnership within Level 3 of the valuation hierarchy [Roll Forward]
Fair value at beginning of period		$ 0	$ (2)
Total gains/(losses) (realized and unrealized) included in earnings(1)	[1]	0	6
Settlements		0	(4)
Fair value at end of period		0	0
The amount of total losses for the period included in earnings attributable to the change in unrealized gains or losses relating to liabilities still held at end of period		0	0
Embedded Derivatives in Commodity Contracts (net)
Derivative assets and liabilities classified by the Partnership within Level 3 of the valuation hierarchy [Roll Forward]
Fair value at beginning of period		(61)	(64)
Total gains/(losses) (realized and unrealized) included in earnings(1)	[1]	(5)	(9)
Settlements		6	12
Fair value at end of period		(60)	(61)
The amount of total losses for the period included in earnings attributable to the change in unrealized gains or losses relating to liabilities still held at end of period		$ (5)	$ (8)

[1] Gains and losses on commodity derivatives classified as Level 3 are recorded in “Product sales” on the Consolidated Statements of Income. Gains and losses on derivatives embedded in commodity contracts are recorded in “Purchased product costs” and “Cost of revenues” on the Consolidated Statements of Income.