Revenue from Contracts with Customers (Contract with Customer, Asset and Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Adoption of ASC606 [Line Items]
Contract liability	$ 9,881	$ 0
Change in contact assets and liabilities, net	(4,970)	$ 0	$ 0
Mid-Stream
Adoption of ASC606 [Line Items]
Contract Assets	13,164			$ 10,798
Change in contract assets	2,366
Contract liability	9,881			12,485
Change in contract liabilities	(2,604)
Contract assets (liabilities), net	3,283			$ (1,687)
Change in contact assets and liabilities, net	$ 4,970