Counterparties representing 10% or more (Details)	Dec. 31, 2018	Dec. 31, 2017
Assets from price risk management activities:
Counterparty A	42.00%	39.00%
Counterparty B	5.00%	12.00%
Counterparty C	15.00%	0.00%
Concentration of Risk, Derivative Instruments, Assets	62.00%	51.00%
Liabilities from price risk management activities: [Abstract]
Counterparty D	56.00%	62.00%
Concentration of Risk, Derivative Instruments, Liabilities	56.00%	62.00%