Derivative Contracts Schedule Of Commodity Derivative Contracts (Details) MMBTU in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) MMBTU $ / MMBTU
Oil Swaps [Member] | Year 2018 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	4.1
Average Swap Price per Unit | $	$ 52.45
Oil Swaps [Member] | Year 2019 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	11.0
Average Swap Price per Unit | $	$ 54.49
Oil Swaps [Member] | Year 2020 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	2.9
Average Swap Price per Unit | $	$ 62.37
Gas Swaps [Member] | Year 2018 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	25.2
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 Basis Swaps [Member] | Year 2018 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	2.3
Weighted-Average Differential | $ / MMBTU	(0.99)
Oil Basis Swaps [Member] | Year 2018 [Member] | NYMEX WTI less Argus WTI Houston [Member]
Derivative [Line Items]
Derivative Volumes	0.1
Weighted-Average Differential | $ / MMBTU	6.30
Oil Basis Swaps [Member] | Year 2019 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	6.6
Weighted-Average Differential | $ / MMBTU	(2.22)
Oil Basis Swaps [Member] | Year 2019 [Member] | NYMEX WTI less Argus WTI Houston [Member]
Derivative [Line Items]
Derivative Volumes	0.4
Weighted-Average Differential | $ / MMBTU	4.35
Oil Basis Swaps [Member] | Year 2020 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	1.5
Weighted-Average Differential | $ / MMBTU	(1.01)
Gas Basis Swaps [Member] | Year 2018 [Member] | NYMEX HH LESS IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	1.8
Weighted-Average Differential | $ / MMBTU	(0.16)