Segments - Financial Data for Each Reportable Segment (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenues and other income		$ 294.8		$ 269.8		$ 583.6	$ 560.6
Net income (loss)		162.0	$ 159.6	107.8	$ 129.0	321.6	236.8
Net income (loss) attributable to Hess Midstream LP		11.0		5.3		19.6	11.8
Depreciation expense		40.4		38.9		80.6	77.4
Proportional share of equity affiliates' depreciation		1.3		1.2		2.6	2.5
Income from equity investments		2.9		0.9		5.6	3.6
Interest expense, net		22.9		23.3		46.0	48.1
Income tax expense (benefit)		3.6		1.7		6.1	3.4
Gain on sale of property, plant and equipment				0.1			0.1
Adjusted EBITDA		230.2		172.8		456.9	368.1
Capital expenditures	[1]	46.4		78.8		69.5	135.8
Interest and Other
Segment Reporting Information [Line Items]
Net income (loss)		(28.1)		(25.6)		(55.8)	(55.9)
Net income (loss) attributable to Hess Midstream LP		(5.8)		(3.1)		(10.0)	(6.7)
Interest expense, net		22.9		23.3		46.0	48.1
Income tax expense (benefit)		3.6		1.7		6.1	3.4
Adjusted EBITDA		(1.6)		(0.6)		(3.7)	(4.4)
Gathering Opco | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income		154.6		136.4		307.3	278.0
Net income (loss)		92.4		71.7		184.8	147.6
Net income (loss) attributable to Hess Midstream LP		8.1		4.6		14.5	9.4
Depreciation expense		25.2		23.7		50.1	47.0
Gain on sale of property, plant and equipment				0.1			0.1
Adjusted EBITDA		117.6		95.3		234.9	194.5
Capital expenditures	[1]	38.2		25.9		57.6	41.7
Processing and Storage | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income		105.3		86.8		208.8	183.8
Net income (loss)		71.6		45.8		142.5	108.5
Net income (loss) attributable to Hess Midstream LP		6.3		2.8		11.1	6.8
Depreciation expense		11.2		11.2		22.4	22.4
Proportional share of equity affiliates' depreciation		1.3		1.2		2.6	2.5
Income from equity investments		2.9		0.9		5.6	3.6
Adjusted EBITDA		84.1		58.2		167.5	133.4
Capital expenditures	[1]	8.1		52.7		11.8	93.8
Terminaling and Export | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income		34.9		46.6		67.5	98.8
Net income (loss)		26.1		15.9		50.1	36.6
Net income (loss) attributable to Hess Midstream LP		2.4		1.0		4.0	2.3
Depreciation expense		4.0		4.0		8.1	8.0
Adjusted EBITDA		30.1		19.9		58.2	44.6
Capital expenditures	[1]	$ 0.1		$ 0.2		$ 0.1	$ 0.3

[1] Includes acquisition, expansion and maintenance capital expenditures, as applicable