Components of Working Capital - Other Current Assets Table (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Other Current Assets [Line Items]
Natural gas liquids inventory		$ 9,421	$ 10,788
Imbalance receivables		7,703	1,640
Prepaid insurance		521	2,955
Contract assets		9,340	0
Other		72	0
Total other current assets	[1]	$ 27,057	$ 15,383

[1] Other current assets includes affiliate amounts of $9.3 million and zero as of June 30, 2018, and December 31, 2017, respectively.