Equity Method Investments - Activity Related to Equity Method Investments (Details) - USD ($) $ in Thousands		12 Months Ended
	Aug. 14, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity Method Investments
Balance at beginning of period		$ 86,077	$ 129,524	$ 103,517
Contributions		77,263	57,039	28,484
Distributions		(1,296)	0	0
Earnings (loss) on equity method investments		1,137	(100,486)	(2,477)
Balance at end of period		163,181	86,077	129,524
Constitution Pipeline Company, LLC
Equity Method Investments
Balance at beginning of period		732	96,850	90,345
Contributions		500	4,350	8,975
Distributions		0	0	0
Earnings (loss) on equity method investments		(1,232)	(100,468)	(2,470)
Balance at end of period		0	732	96,850
Meade Pipeline Co LLC
Equity Method Investments
Balance at beginning of period		85,345	32,674	13,172
Contributions	$ 17,800	76,763	52,689	19,509
Distributions		(1,296)	0	0
Earnings (loss) on equity method investments		2,369	(18)	(7)
Balance at end of period		$ 163,181	$ 85,345	$ 32,674