Acquisitions - Consolidated Statements of Cash Flows (Detail) - USD ($) $ in Millions		3 Months Ended									9 Months Ended			12 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019		Jun. 30, 2019	[1]	Mar. 31, 2019		Sep. 30, 2020	Sep. 30, 2019		Dec. 31, 2019
Cash flows from operating activities
Net income		$ 115.8	$ 107.8	$ 129.0	$ 87.4	[1]	$ 74.4		$ 80.8	[1]	$ 352.6	$ 242.6	[1]
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation expense		39.5			36.0	[1]					116.9	105.0	[1]
(Gain) loss on interest rate swaps											(0.4)	(0.6)	[1]
Amortization of deferred financing costs											5.1	3.8	[1]
Equity-based compensation expense											1.2	1.1	[1]
Changes in assets and liabilities:
Accounts receivable – affiliate											(4.9)	(7.6)	[1]
Other current and noncurrent assets											(3.4)	(4.7)	[1]
Accounts payable – trade											9.5	3.7	[1]
Accounts payable – affiliate											(0.5)	(1.5)	[1]
Accrued liabilities											(12.6)
Other current and noncurrent liabilities											(1.0)	(2.8)	[1]
Net cash provided by (used in) operating activities											467.2	334.4	[1]
(Income) loss from equity investments		(3.6)			(0.5)	[1]					(7.2)	(0.5)	[1]
(Increase) decrease in capitalized interest	[1]											4.1
Cash flows from investing activities
Payments for equity investments	[1]											(33.0)
Acquisitions from Hess												(68.9)
Acquisitions	[1]											(89.2)
Additions to property, plant and equipment											(246.0)	(194.9)	[1]
Net cash provided by (used in) investing activities											(245.9)	(386.0)	[1]
Cash flows from financing activities
Net proceeds from (repayments of) bank borrowings with maturities of 90 days or less											146.0	176.0	[1]
Repayments of bank borrowings with maturities of greater than 90 days	[1]											(7.5)
Capital distribution to Hess associated with acquisitions	[1]											(156.1)
Distributions to shareholders/unitholders											(23.5)	(63.0)	[1]
Distributions to noncontrolling interest											(344.4)
Net cash provided by (used in) financing activities											(221.6)	(50.6)	[1]
Increase (decrease) in cash and cash equivalents											(0.3)	(102.2)	[1]
Cash and cash equivalents, beginning of period				$ 3.3					109.3	[1]	3.3	109.3	[1]	$ 109.3	[1]
Cash and cash equivalents, end of period		$ 3.0			7.1	[1]					$ 3.0	7.1	[1]	3.3
Partnership as Previously Reported
Cash flows from operating activities
Net income					100.4							286.6
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation expense					34.5							101.1
Amortization of deferred financing costs												0.9
Equity-based compensation expense												1.1
Changes in assets and liabilities:
Accounts receivable – affiliate												(5.2)
Other current and noncurrent assets												(5.0)
Accounts payable – trade												2.2
Accounts payable – affiliate												4.3
Accrued liabilities												9.2
Other current and noncurrent liabilities												(2.5)
Net cash provided by (used in) operating activities												392.2
(Income) loss from equity investments					(0.5)							(0.5)
Cash flows from investing activities
Payments for equity investments												(33.0)
Acquisitions												(61.0)
Additions to property, plant and equipment												(184.4)
Net cash provided by (used in) investing activities												(278.4)
Cash flows from financing activities
Net proceeds from (repayments of) bank borrowings with maturities of 90 days or less												11.0
Distributions to shareholders/unitholders												(63.0)
Distributions to general partner												(2.5)
Distributions to noncontrolling interest												(152.4)
Contributions from noncontrolling interest												76.3
Net cash provided by (used in) financing activities												(130.6)
Increase (decrease) in cash and cash equivalents												(16.8)
Cash and cash equivalents, beginning of period									20.3			20.3		20.3
Cash and cash equivalents, end of period					3.5							3.5
Restatement Adjustment | Acquisition of HIP
Cash flows from operating activities
Net income					(13.0)							(44.0)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation expense					1.5							3.9
(Gain) loss on interest rate swaps												(0.6)
Amortization of deferred financing costs												2.9
Changes in assets and liabilities:
Accounts receivable – affiliate												(2.4)
Other current and noncurrent assets												0.3
Accounts payable – trade												1.5
Accounts payable – affiliate												(5.8)
Accrued liabilities												(9.2)
Other current and noncurrent liabilities												(0.3)
Net cash provided by (used in) operating activities												(57.8)
(Increase) decrease in capitalized interest												4.1
Cash flows from investing activities
Acquisitions from Hess												(68.9)
Acquisitions												(28.2)
Additions to property, plant and equipment												(10.5)
Net cash provided by (used in) investing activities												(107.6)
Cash flows from financing activities
Net proceeds from (repayments of) bank borrowings with maturities of 90 days or less												165.0
Repayments of bank borrowings with maturities of greater than 90 days												(7.5)
Capital distribution to Hess associated with acquisitions												(156.1)
Distributions to general partner												2.5
Distributions to noncontrolling interest												152.4
Contributions from noncontrolling interest												(76.3)
Net cash provided by (used in) financing activities												80.0
Increase (decrease) in cash and cash equivalents												(85.4)
Cash and cash equivalents, beginning of period									$ 89.0			89.0		$ 89.0
Cash and cash equivalents, end of period					$ 3.6							$ 3.6

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