Counterparties representing 10% or more (Details)	Dec. 31, 2013	Dec. 31, 2012
Assets from price risk management activities:
Counterparty A	53.00%	0.00%
Counterparty B	5.00%	21.00%
Counterparty C	5.00%	11.00%
Counterparty D	4.00%	13.00%
Counterparty E	0.00%	10.00%
Concentration of Risk, Derivative Instruments, Assets	67.00%	55.00%
Liabilities from price risk management activities: [Abstract]
Counterparty F	43.00%	0.00%
Counterparty G	11.00%	0.00%
Counterparty H	6.00%	24.00%
Counterparty I for PRM Liabs	5.00%	10.00%
Counterparty A for PRM Liabs	2.00%	14.00%
Concentration of Risk, Derivative Instruments, Liabilities	67.00%	48.00%