Derivatives (Net Derivatives as Reflected on the Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Successor [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 4,807
Successor [Member] | Other Current Assets [Member] | Heating Oil [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	4,646
Successor [Member] | Coal Derivative Assets [Member] | Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	262
Successor [Member] | Coal Derivative Liabilities [Member] | Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (101)
Predecessor [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet		$ 9,052
Predecessor [Member] | Other Current Assets [Member] | Heating Oil [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet		1,017
Predecessor [Member] | Coal Derivative Assets [Member] | Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet		8,035
Predecessor [Member] | Coal Derivative Liabilities [Member] | Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet		$ 0