Derivative Instruments Volume of Derivative Activity (Details) $ in Thousands, gal in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) gal
PESCO [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months | $	$ (570)
Sharp Energy Inc [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months | $	$ 392
Sharp Energy Inc [Member] | Swap [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	4.4
Sharp Energy Inc [Member] | Put Option [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	0.3