Derivative Contracts Schedule Of Commodity Derivative Contracts (Details) MMBTU in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) MMBTU $ / MMBTU
Gas Swaps [Member] | Year 2018 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	82.5
Average Swap Price per Unit | $	$ 2.99
Gas Swaps [Member] | Year 2018 (July through December) [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	1.8
Average Swap Price per Unit | $	$ 3.01
Gas Swaps [Member] | Year 2019 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	43.8
Average Swap Price per Unit | $	$ 2.86
Oil Swaps [Member] | Year 2018 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	12.7
Average Swap Price per Unit | $	$ 52.48
Oil Swaps [Member] | Year 2019 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	9.5
Average Swap Price per Unit | $	$ 52.66
Oil Basis Swaps [Member] | Year 2018 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	5.5
Weighted-Average Differential | $ / MMBTU	(1.06)
Oil Basis Swaps [Member] | Year 2018 (July through December) [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	0.9
Weighted-Average Differential | $ / MMBTU	(0.71)
Oil Basis Swaps [Member] | Year 2019 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	4.7
Weighted-Average Differential | $ / MMBTU	(0.77)
Gas Basis Swaps [Member] | Year 2018 [Member] | NYMEX HH LESS IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	5.5
Weighted-Average Differential | $ / MMBTU	(0.16)