Risk Management (Fair Value of Derivatives) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivative Assets [Abstract]
Derivative asset, fair value	$ 26,613
Derivative asset, liability	(2,662)
Derivative asset	15,452
Long–term derivative asset	8,499
Derivative asset, Net recorded fair value	23,951
Derivative Liabilities [Abstract]
Derivative liability, fair value	3,827
Derivative liability, asset	(2,662)
Derivative liability	1,165
Derivative liability, Net recorded fair value	1,165
Current Derivatives Asset [Member]
Derivative Assets [Abstract]
Derivative asset, fair value	18,048
Derivative asset, liability	(2,596)
Derivative asset	15,452
Noncurrent Derivative Asset [Member]
Derivative Assets [Abstract]
Derivative asset, fair value	8,565
Derivative asset, liability	(66)
Long–term derivative asset	8,499
Current Derivatives Liability [Member]
Derivative Liabilities [Abstract]
Derivative liability, fair value	3,761
Derivative liability, asset	(2,596)
Derivative liability	1,165
Noncurrent Derivative Liability [Member]
Derivative Liabilities [Abstract]
Derivative liability, fair value	66
Derivative liability, asset	$ (66)
Predecessor
Derivative Assets [Abstract]
Derivative asset, fair value		$ 3,402
Derivative asset, liability		(350)
Derivative asset		3,052
Derivative Liabilities [Abstract]
Derivative liability, fair value		746
Derivative liability, asset		(350)
Derivative liability		$ 396