Derivative Instruments (Schedule of Contingent Consideration) (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2018 USD ($) $ / bbls $ / MMBTU
ExL Acquisition
Embedded Derivative [Line Items]
Threshold Price per Bbl for Additional Payments for Acquisition	50.00
Potential Additional Annual Payments for Acquisition | $	$ (50,000)
Contingent Consideration, Range of Outcomes, Value, High | $	(125,000)
Utica Shale Divestiture
Embedded Derivative [Line Items]
Potential Additional Annual Proceeds From Divestiture | $	$ 5,000
Utica Shale Divestiture | FY 2018 [Member]
Embedded Derivative [Line Items]
Threshold Price Per Bbl For Additional Proceeds From Divestiture	50.00
Utica Shale Divestiture | FY 2019 [Member]
Embedded Derivative [Line Items]
Threshold Price Per Bbl For Additional Proceeds From Divestiture	53.00
Utica Shale Divestiture | FY 2020 [Member]
Embedded Derivative [Line Items]
Threshold Price Per Bbl For Additional Proceeds From Divestiture	56.00
Marcellus Shale Divestiture
Embedded Derivative [Line Items]
Contingent Consideration, Range of Outcomes, Value, High | $	$ (7,500)
Potential Additional Annual Proceeds From Divestiture | $	$ 3,000
Marcellus Shale Divestiture | FY 2018 [Member]
Embedded Derivative [Line Items]
Threshold Price per MMBtu for Additional Payments from Divestiture | $ / MMBTU	3.13
Marcellus Shale Divestiture | FY 2019 [Member]
Embedded Derivative [Line Items]
Threshold Price per MMBtu for Additional Payments from Divestiture | $ / MMBTU	3.18
Marcellus Shale Divestiture | FY 2020 [Member]
Embedded Derivative [Line Items]
Threshold Price per MMBtu for Additional Payments from Divestiture | $ / MMBTU	3.30
Niobrara Divestiture
Embedded Derivative [Line Items]
Potential Additional Annual Proceeds From Divestiture | $	$ 5,000
Niobrara Divestiture | FY 2018 [Member]
Embedded Derivative [Line Items]
Threshold Price Per Bbl For Additional Proceeds From Divestiture	55.00
Niobrara Divestiture | FY 2019 [Member]
Embedded Derivative [Line Items]
Threshold Price Per Bbl For Additional Proceeds From Divestiture	55.00
Niobrara Divestiture | FY 2020 [Member]
Embedded Derivative [Line Items]
Threshold Price Per Bbl For Additional Proceeds From Divestiture	60.00