Concentration of Credit Risk and Major Customers (Tables)

12 Months Ended

Dec. 31, 2018

Risks and Uncertainties [Abstract]

Schedule of Concentration of Credit Risk

Concentration of credit risk is summarized below:

	December 31,
	2018		2017
Thermal coal utilities	$	61,218	$	69,550
Coal exporters and distributors	22,972		56,146
Steel and coke producers	661		—
Other	2,738		5,849
Total Accounts Receivable Trade	$	87,589	$	131,545