Related Party transactions - Revenue from Contracts with Customers on Disaggregated Basis (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
Disaggregation Of Revenue [Line Items]
Affiliate services									$ 847.6	$ 712.0	[1]	$ 579.5	[1]
Other income									0.7	0.7	[1]
Total revenues	$ 253.5	$ 214.9	$ 190.3	$ 189.6	$ 185.9	$ 183.8	$ 176.5	$ 166.5	848.3	712.7	[1]	579.5	[1]
Oil and Gas Gathering Services
Disaggregation Of Revenue [Line Items]
Affiliate services									345.6	324.9		271.6
Water Gathering and Disposal Services
Disaggregation Of Revenue [Line Items]
Affiliate services									77.3	50.3		13.9
Processing and Storage Services
Disaggregation Of Revenue [Line Items]
Affiliate services									294.7	251.4		227.3
Terminaling and Export Services
Disaggregation Of Revenue [Line Items]
Affiliate services									$ 130.0	$ 85.4		$ 66.7

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