Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Quarterly Financial Data
Revenues	$ 623		$ 642	[1]	$ 569	[1]	$ 546	[1]	$ 1,114	[1]	$ 1,094	[1]	$ 614	[1]	$ 427	[1]	$ 2,380	[2]	$ 3,249	[2]	$ 1,669	[2]
Operating expenses	227		236	[1]	221	[1]	201	[1]	179	[1]	199	[1]	171	[1]	142	[1]	885	[1],[2]	691	[1],[2]	560	[2]
Operating income	224		215	[1]	180	[1]	177	[1]	179	[1]	147	[1]	146	[1]	131	[1]	796	[2]	603	[2]	448	[2]
Net earnings	171		166	[1]	132	[1]	131	[1]	53	[1]	90	[1]	90	[1]	73	[1]	600	[2],[3],[4]	306	[2],[3],[4]	277	[2],[3],[4],[5]
Limited partners’ interest in net earnings	$ 161		$ 160		$ 138		$ 125		$ 47	[6]	$ 97	[6]	$ 70	[6]	$ 55	[6]	$ 584		$ 267		$ 187
Net earnings (loss) per limited partner unit:
Common - basic (dollars per unit)	$ 0.66	[6]	$ 0.68	[6]	$ 0.63	[6]	$ 0.59	[6]	$ 0.25	[6]	$ 0.90	[6]	$ 0.63	[6]	$ 0.51	[6]	$ 2.57	[7]	$ 2.11	[7]	$ 1.87	[7]
Common - diluted (dollars per unit)	$ 0.66	[6]	$ 0.68	[6]	$ 0.63	[6]	$ 0.59	[6]	$ 0.25	[6]	$ 0.90	[6]	$ 0.63	[6]	$ 0.51	[6]	$ 2.57	[7]	$ 2.11	[7]	$ 1.87	[7]
Natural Gas, Midstream [Member]
Quarterly Financial Data
Cost of Goods and Services Sold	$ 40	[8]	$ 73	[8]	$ 45	[8]	$ 48	[8]	$ 86	[8]	$ 64	[8]	$ 56	[8]	$ 59	[8]	$ 206	[2]	$ 265	[2],[8]	$ 2	[2]
Oil and Gas, Purchased [Member]
Quarterly Financial Data
Cost of Goods and Services Sold									$ 528	[8],[9]	$ 554	[8],[9]	$ 162	[8],[9]	$ 0	[8],[9]	$ 0	[2],[10]	$ 1,244	[2],[8],[9],[10]	$ 316	[2],[10]

[1] Adjusted to include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[2] All periods include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[3] Adjusted to include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[4] Adjusted to include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[5] All periods include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[6] The sum of four quarters may not equal annual results due to rounding or the quarterly number of units outstanding.

[7] Amounts may not recalculate due to rounding of dollar and unit information.

[8] Excludes direct operating expenses incurred across our operating segments and depreciation and amortization expenses.

[9] Due to the adoption of ASC 606 effective January 1, 2018, the revenues and costs associated with our fuel purchase and supply arrangements for the year ended December 31, 2018 were netted. See Note 1 for further discussion.

[10] Due to the adoption of ASC 606 effective January 1, 2018, the revenues and costs associated with our fuel purchase and supply arrangements for year ended December 31, 2018 were netted. See Note 1 for further discussion.