CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (UNAUDITED) - USD ($) $ in Millions		Total		Limited Partner Common Unitholders Public	Limited Partner Common Unitholders Affiliate	Limited Partner Subordinated Unitholders Affiliate	Limited Partner Class A Shares	General Partner	Noncontrolling Interest	Accumulated Other Comprehensive Income	Net Parent Investment
Balance, beginning of period at Dec. 31, 2018		$ 1,876.1	[1]	$ 357.1	$ 39.5	$ 105.3		$ 14.9	$ 2,194.1	$ 1.2	$ (836.0)
Net income		80.8	[1]	5.3	3.4	8.6		0.8	77.2		(14.5)
Equity-based compensation		0.3	[1]	0.3
Distributions to unitholders		(20.2)	[1]	(6.3)	(3.8)	(10.1)
Distributions to general partner								(0.6)			0.6
Distributions to noncontrolling interest									(57.1)		57.1
Contributions from noncontrolling interest									55.5		(55.5)
Other comprehensive income (loss)		(0.2)	[1]							(0.2)
Acquisition of HessWater Services		(225.0)	[1]								(225.0)
Balance, end of period at Mar. 31, 2019		1,711.8	[1]	356.4	39.1	103.8		15.1	2,269.7	1.0	(1,073.3)
Balance, beginning of period at Dec. 31, 2018		1,876.1	[1]	357.1	39.5	105.3		14.9	2,194.1	1.2	(836.0)
Net income	[1]	242.6
Other comprehensive income (loss)	[1]	(0.6)
Balance, end of period at Sep. 30, 2019		1,831.2	[1]	354.2	37.5	99.2		15.5	2,350.6	0.6	(1,026.4)
Balance, beginning of period at Mar. 31, 2019		1,711.8	[1]	356.4	39.1	103.8		15.1	2,269.7	1.0	(1,073.3)
Net income		74.4	[1]	4.9	3.0	7.9		1.0	74.1		(16.5)
Equity-based compensation		0.3	[1]	0.3
Distributions to unitholders		(21.0)	[1]	(6.5)	(4.0)	(10.5)
Distributions to general partner								(0.8)			0.8
Distributions to noncontrolling interest									(49.0)		49.0
Contributions from noncontrolling interest									12.8		(12.8)
Other comprehensive income (loss)		(0.2)	[1]							(0.2)
Balance, end of period at Jun. 30, 2019		1,765.3	[1]	355.1	38.1	101.2		15.3	2,307.6	0.8	(1,052.8)
Net income		87.4	[1]	5.5	3.4	8.9		1.3	81.3		(13.0)
Equity-based compensation		0.5	[1]	0.5
Distributions to unitholders		(21.8)	[1]	(6.9)	(4.0)	(10.9)
Distributions to general partner								(1.1)			1.1
Distributions to noncontrolling interest									(46.3)		46.3
Contributions from noncontrolling interest									8.0		(8.0)
Other comprehensive income (loss)		(0.2)	[1]							(0.2)
Balance, end of period at Sep. 30, 2019		1,831.2	[1]	$ 354.2	$ 37.5	$ 99.2		$ 15.5	2,350.6	0.6	$ (1,026.4)
Balance, beginning of period at Dec. 31, 2019		1,332.1					$ 131.1		1,200.6	0.4
Net income		129.0					6.5		122.5
Equity-based compensation		0.5					0.5
Distributions to unitholders		(121.0)					(7.6)		(113.4)
Other comprehensive income (loss)		(0.2)								(0.2)
Balance, end of period at Mar. 31, 2020		1,340.4					130.5		1,209.7	0.2
Balance, beginning of period at Dec. 31, 2019		1,332.1					131.1		1,200.6	0.4
Net income		352.6
Other comprehensive income (loss)		(0.4)
Balance, end of period at Sep. 30, 2020		1,319.2					126.2		1,193.0
Balance, beginning of period at Mar. 31, 2020		1,340.4					130.5		1,209.7	0.2
Net income		107.8					5.3		102.5
Equity-based compensation		0.3					0.3
Distributions to unitholders		(122.7)					(7.9)		(114.8)
Other comprehensive income (loss)		(0.2)								$ (0.2)
Acquisition of HessWater Services		1.6							1.6
Balance, end of period at Jun. 30, 2020		1,327.2					128.2		1,199.0
Net income		115.8					5.6		110.2
Equity-based compensation		0.4					0.4
Distributions to unitholders		(124.2)					(8.0)		(116.2)
Balance, end of period at Sep. 30, 2020		$ 1,319.2					$ 126.2		$ 1,193.0

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