Segments - Financial Data for Each Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended									9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019		Jun. 30, 2019	[1]	Mar. 31, 2019	[1]	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues and other income	$ 264.8			$ 214.9	[1]					$ 825.4	$ 594.8	[1]
Net income (loss)	115.8	$ 107.8	$ 129.0	87.4	[1]	$ 74.4		$ 80.8		352.6	242.6	[1]
Net income (loss) attributable to Hess Midstream LP	5.6			19.1	[1]					17.4	54.0	[1]
Depreciation expense	39.5			36.0	[1]					116.9	105.0	[1]
Proportional share of equity affiliates' depreciation	1.3			0.5						3.8	0.5
Income from equity investments	3.6			0.5	[1]					7.2	0.5	[1]
Interest expense, net	23.2			12.4	[1]					71.3	44.2	[1]
Income tax expense (benefit)	1.8									5.2
Gain on sale of property, plant and equipment										0.1
Adjusted EBITDA	181.6			136.3						549.7	392.3
Capital expenditures	66.4			112.1						202.2	308.0
Interest and Other
Segment Reporting Information [Line Items]
Net income (loss)	(25.3)			(16.2)						(81.2)	(52.9)
Net income (loss) attributable to Hess Midstream LP	(3.2)			(1.6)						(9.9)	(5.0)
Interest expense, net	23.2			12.4						71.3	44.2
Income tax expense (benefit)	1.8									5.2
Adjusted EBITDA	(0.3)			(3.8)						(4.7)	(8.7)
Gathering Opco | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income	142.9			105.9						420.9	298.0
Net income (loss)	72.4			46.5						220.0	132.5
Net income (loss) attributable to Hess Midstream LP	4.5			9.1						13.9	25.8
Depreciation expense	24.2			20.8						71.2	59.5
Gain on sale of property, plant and equipment										0.1
Adjusted EBITDA	96.6			67.3						291.1	192.0
Capital expenditures	30.2			96.7						71.9	284.2
Processing and Storage | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income	90.2			74.0						274.0	208.0
Net income (loss)	50.7			42.8						159.2	124.2
Net income (loss) attributable to Hess Midstream LP	3.2			8.8						10.0	25.4
Depreciation expense	11.2			11.2						33.6	33.5
Proportional share of equity affiliates' depreciation	1.3			0.5						3.8	0.5
Income from equity investments	3.6									7.2
Adjusted EBITDA	63.2			54.5						196.6	158.2
Capital expenditures	36.1			15.0						129.9	23.7
Terminaling and Export | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income	31.7			35.0						130.5	88.8
Net income (loss)	18.0			14.3						54.6	38.8
Net income (loss) attributable to Hess Midstream LP	1.1			2.8						3.4	7.8
Depreciation expense	4.1			4.0						12.1	12.0
Adjusted EBITDA	22.1			18.3						66.7	50.8
Capital expenditures	$ 0.1			$ 0.4						$ 0.4	$ 0.1

[1] The financial information presented in this report has been retrospectively adjusted for the acquisition of Hess Infrastructure Partners LP.