Variable Interest Entities (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2016	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Acquisitions, earnout and capital investments		$ 128,141	$ 127,899
Earnings in equity investments		26,157	23,144
Distributions received		(48,946)	(36,578)
Maximum exposure to loss		105,352	$ 114,465
Carnero Gathering, Joint Venture
Variable Interest Entity [Line Items]
Payments to acquire interest in joint venture	$ 37,000	124,100
Debt incurred		$ 0