Acquisitions - Consolidated Statements of Operations (Detail) - USD ($) $ / shares in Units, shares in Millions, $ 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
Revenues and other income
Affiliate services		$ 264.7			$ 214.9	[1]					$ 825.1	$ 594.5	[1]
Type of Revenue [Extensible List]		hesm:AffiliateServicesMember			hesm:AffiliateServicesMember	[1]					hesm:AffiliateServicesMember	hesm:AffiliateServicesMember	[1]
Total revenues		$ 264.8			$ 214.9	[1]					$ 825.4	$ 594.8	[1]
Other income		0.1									0.3	0.3	[1]
Costs and expenses
Operating and maintenance expenses (exclusive of depreciation shown separately below)		83.9			71.9	[1]					270.8	184.1	[1]
Depreciation expense		39.5			36.0	[1]					116.9	105.0	[1]
General and administrative expenses		4.2			7.7	[1]					15.9	19.4	[1]
Total costs and expenses		127.6			115.6	[1]					403.6	308.5	[1]
Income from operations		137.2			99.3	[1]					421.8	286.3	[1]
Earnings 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]
Net income		115.8	$ 107.8	$ 129.0	87.4	[1]	$ 74.4		$ 80.8		352.6	242.6	[1]
Less: Net income (loss) attributable to net parent investment	[1]				(13.0)							(44.0)
Less: Net income (loss) attributable to noncontrolling interest		110.2			81.3	[1]					335.2	232.6	[1]
Net income attributable to Hess Midstream LP		5.6			19.1	[1]					17.4	54.0	[1]
Less: General partner's interest in net income	[1]				1.3							3.1
Limited partners' interest in net income		$ 5.6			$ 17.8	[1]					$ 17.4	$ 50.9	[1]
Common Units
Net income attributable to Hess Midstream LP per limited partner unit (basic and diluted):
Net income attributable to Hess Midstream Partners per limited partner unit	[1]				$ 0.33							$ 0.93
Weighted average limited partner units outstanding, Basic:
Units outstanding prior to the Restructuring, Basic	[1]				27.3							27.3
Weighted average limited partner units outstanding, Diluted:
Units outstanding prior to the Restructuring, Diluted	[1]				27.5							27.5
Subordinated Units
Net income attributable to Hess Midstream LP per limited partner unit (basic and diluted):
Net income attributable to Hess Midstream Partners per limited partner unit	[1]				$ 0.33							$ 0.93
Weighted average limited partner units outstanding, Basic:
Units outstanding prior to the Restructuring, Basic	[1]				27.3							27.3
Weighted average limited partner units outstanding, Diluted:
Units outstanding prior to the Restructuring, Diluted	[1]				27.3							27.3
Partnership as Previously Reported
Revenues and other income
Affiliate services					$ 195.4							$ 542.1
Type of Revenue [Extensible List]					hesm:AffiliateServicesMember							hesm:AffiliateServicesMember
Total revenues					$ 195.4							$ 542.4
Other income												0.3
Costs and expenses
Operating and maintenance expenses (exclusive of depreciation shown separately below)					56.5							142.0
Depreciation expense					34.5							101.1
General and administrative expenses					3.9							11.6
Total costs and expenses					94.9							254.7
Income from operations					100.5							287.7
Earnings from equity investments					0.5							0.5
Interest expense, net					0.6							1.6
Net income					100.4							286.6
Less: Net income (loss) attributable to noncontrolling interest					81.3							232.6
Net income attributable to Hess Midstream LP					19.1							54.0
Less: General partner's interest in net income					1.3							3.1
Limited partners' interest in net income					$ 17.8							$ 50.9
Partnership as Previously Reported | Common Units
Net income attributable to Hess Midstream LP per limited partner unit (basic and diluted):
Net income attributable to Hess Midstream Partners per limited partner unit					$ 0.33							$ 0.93
Weighted average limited partner units outstanding, Basic:
Units outstanding prior to the Restructuring, Basic					27.3							27.3
Weighted average limited partner units outstanding, Diluted:
Units outstanding prior to the Restructuring, Diluted					27.5							27.5
Partnership as Previously Reported | Subordinated Units
Net income attributable to Hess Midstream LP per limited partner unit (basic and diluted):
Net income attributable to Hess Midstream Partners per limited partner unit					$ 0.33							$ 0.93
Weighted average limited partner units outstanding, Basic:
Units outstanding prior to the Restructuring, Basic					27.3							27.3
Weighted average limited partner units outstanding, Diluted:
Units outstanding prior to the Restructuring, Diluted					27.3							27.3
Restatement Adjustment | Acquisition of HIP
Revenues and other income
Affiliate services					$ 19.5							$ 52.4
Type of Revenue [Extensible List]					hesm:AffiliateServicesMember							hesm:AffiliateServicesMember
Total revenues					$ 19.5							$ 52.4
Costs and expenses
Operating and maintenance expenses (exclusive of depreciation shown separately below)					15.4							42.1
Depreciation expense					1.5							3.9
General and administrative expenses					3.8							7.8
Total costs and expenses					20.7							53.8
Income from operations					(1.2)							(1.4)
Interest expense, net					11.8							42.6
Net income					(13.0)							(44.0)
Less: Net income (loss) attributable to net parent investment					$ (13.0)							$ (44.0)

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