Segments - Financial Data for Each Reportable Segment (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues and other income		$ 253.5	$ 214.9	$ 190.3	$ 189.6	$ 185.9	$ 183.8	$ 176.5	$ 166.5	$ 848.3		$ 712.7	[1]	$ 579.5	[1]
Net income (loss)		75.1	87.4	74.4	80.8	78.9	86.1	82.8	77.7	317.7		325.5	[1]	242.0	[1]
Net income (loss) attributable to Hess Midstream LP		$ 16.1	$ 19.1	$ 16.8	$ 18.1	$ 17.2	$ 18.8	$ 17.8	$ 17.0	70.1		70.8	[1]	41.2	[1]
Depreciation expense										142.5		126.9	[1]	116.5	[1]
Proportional share of equity affiliates' depreciation										2.0
Income from equity investments										3.4
Interest expense, net										62.4		53.3	[1]	25.8	[1]
Gain on sale of property, plant and equipment	[1]											0.6		4.7
Income tax expense (benefit)										(0.1)
Transaction costs										26.2
Adjusted EBITDA										550.7		505.1		379.6
Capital expenditures										416.3	[2]	271.3		118.3
Interest and Other
Segment Reporting Information [Line Items]
Net income (loss)										(99.2)		(59.0)		(28.3)
Net income (loss) attributable to Hess Midstream LP										(9.6)		(5.6)		(3.3)
Interest expense, net										62.4		53.3		25.8
Gain on sale of property, plant and equipment												0.6		4.7
Income tax expense (benefit)										(0.1)
Transaction costs										26.2
Adjusted EBITDA										(10.7)		(6.3)		(7.2)
Gathering Opco | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income										422.9		375.2		285.5
Net income (loss)										186.0		199.6		132.1
Net income (loss) attributable to Hess Midstream LP										34.6		38.4		23.3
Depreciation expense										81.6		67.2		57.8
Adjusted EBITDA										267.6		266.8		189.9
Capital expenditures										373.6	[2]	257.0		77.8
Processing and Storage | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income										295.3		251.4		227.3
Net income (loss)										176.1		148.8		123.8
Net income (loss) attributable to Hess Midstream LP										34.6		30.7		18.8
Depreciation expense										44.7		43.9		43.6
Proportional share of equity affiliates' depreciation										2.0
Income from equity investments										3.4
Adjusted EBITDA										222.8		192.7		167.4
Capital expenditures										42.5	[2]	10.0		15.9
Terminaling and Export | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income										130.1		86.1		66.7
Net income (loss)										54.8		36.1		14.4
Net income (loss) attributable to Hess Midstream LP										10.5		7.3		2.4
Depreciation expense										16.2		15.8		15.1
Adjusted EBITDA										71.0		51.9		29.5
Capital expenditures										$ 0.2	[2]	$ 4.3		$ 24.6

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

[2] Includes acquisition, expansion and maintenance capital expenditures.