Derivative Contracts Schedule Of Commodity Derivative Contracts (Details) MMBTU in Millions	9 Months Ended
	Sep. 30, 2017 USD ($) MMBTU $ / MMBTU
Oil Basis Swaps [Member] | Production [Member] | Year 2017 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	1.1
Weighted-Average Differential | $ / MMBTU	(0.67)
Oil Basis Swaps [Member] | Production [Member] | Year 2018 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	7.3
Weighted-Average Differential | $ / MMBTU	(1.06)
Oil Basis Swaps [Member] | Production [Member] | Year 2018 (July through December) [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	0.6
Weighted-Average Differential | $ / MMBTU	(0.81)
Oil Basis Swaps [Member] | Production [Member] | Year 2019 [Member] | NYMEX WTI less Argus WTI Midland [Member]
Derivative [Line Items]
Derivative Volumes	2.2
Weighted-Average Differential | $ / MMBTU	(0.98)
Gas Swaps [Member] | Production [Member] | Year 2017 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	24.8
Average Swap Price per Unit | $	$ 2.87
Gas Swaps [Member] | Production [Member] | Year 2017 [Member] | IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	6.4
Average Swap Price per Unit | $	$ 2.49
Gas Swaps [Member] | Production [Member] | Year 2018 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	105.9
Average Swap Price per Unit | $	$ 2.99
Gas Swaps [Member] | Production [Member] | Year 2019 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	14.6
Average Swap Price per Unit | $	$ 2.87
Gas Swaps [Member] | Storage [Member] | Year 2017 [Member] | IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	1.5
Average Swap Price per Unit | $	$ 2.88
Gas Swaps [Member] | Storage [Member] | Year 2018 [Member] | IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	0.4
Average Swap Price per Unit | $	$ 3.05
Oil Swaps [Member] | Production [Member] | Year 2017 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	3.6
Average Swap Price per Unit | $	$ 51.51
Oil Swaps [Member] | Production [Member] | Year 2018 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	14.6
Average Swap Price per Unit | $	$ 52.42
Oil Swaps [Member] | Production [Member] | Year 2019 [Member] | NYMEX WTI [Member]
Derivative [Line Items]
Derivative Volumes	3.7
Average Swap Price per Unit | $	$ 50.30
Gas Collars [Member] | Production [Member] | Year 2017 [Member] | NYMEX HH [Member]
Derivative [Line Items]
Derivative Volumes	2.8
Derivative Average Price Floor | $	$ 2.50
Derivative Average Price Ceiling | $	$ 3.50
Gas Basis Swaps [Member] | Production [Member] | Year 2018 [Member] | NYMEX HH LESS IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	7.3
Weighted-Average Differential | $ / MMBTU	(0.16)
Gas Purchase Swaps [Member] | Storage [Member] | Year 2018 [Member] | IFNPCR [Member]
Derivative [Line Items]
Derivative Volumes	1.1
Average Swap Price per Unit | $	$ 2.68