Derivative Financial Instruments Additional Information (Details) $ in Millions	3 Months Ended
	Jun. 30, 2018 USD ($)
Derivatives in Place for Anticipated Production
Gain on early settlement of derivative basis protection positions	$ 11.3
Natural Gas [Member]
Derivatives in Place for Anticipated Production
Gain on early settlement of derivative basis protection positions	1.0
Crude Oil [Member]
Derivatives in Place for Anticipated Production
Gain on early settlement of derivative basis protection positions	$ 10.3