Partners' Capital (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended						9 Months Ended
	Jan. 25, 2017	Oct. 14, 2015	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2019	Dec. 06, 2016
Limited Partners' Capital Account [Line Items]
Class B preferred units, outstanding					31,310,896					0
Common units, outstanding					16,486,239					20,089,827
Units, issued					16,486,239					20,089,827
Class B preferred units, issued					31,310,896					0
Class B preferred units
Limited Partners' Capital Account [Line Items]
Units sold (in units)		19,444,445
Price per unit sold		$ 18.00
Proceeds from preferred units sold		$ 350.0
Percent of consideration paid		2.25%
Class B preferred units, issued											9,851,996
Class B preferred units | Settlement Agreement with Stonepeak Catarina Holdings LLC
Limited Partners' Capital Account [Line Items]
Class B preferred units, issued	1,704,446
Class B preferred units, unit price	$ 11.29
Class C preferred units
Limited Partners' Capital Account [Line Items]
Class B preferred units, outstanding										32,250,223
Common units
Limited Partners' Capital Account [Line Items]
Common units, outstanding										20,089,827
Units sold (in units)			901,741	887,269	787,750	334,010	224,342	210,978	220,214
Unvested restricted common units | LTIP
Limited Partners' Capital Account [Line Items]
Common units, outstanding										1,158,793