Derivatives Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Derivative [Line Items]

Schedule of derivative financial instruments

	Swaps
Settlement Period	Notional Amount	Weighted-Average per Barrel
2017 swap positions	363	$	55.00
Total	363	$	55.00

Schedule of offsetting and balance sheet presentation

	March 31, 2017
	Gross Amounts Recognized				Gross Amounts Offset in the Consolidated Balance Sheet				Net Amounts Presented in the Consolidated Balance Sheet
	Assets		Liabilities		Assets		Liabilities		Assets		Liabilities
International coal forward contracts	$	—	$	—	$	—	$	—	$	—	$	—
WTI derivative financial instruments		—		(1,257)		—		—		—		(1,257)
Total	$	—	$	(1,257)	$	—	$	—	$	—	$	(1,257)

	December 31, 2016
	Gross Amounts Recognized				Gross Amounts Offset in the Consolidated Balance Sheet				Net Amounts Presented in the Consolidated Balance Sheet
	Assets		Liabilities		Assets		Liabilities		Assets		Liabilities
International coal forward contracts	$	—	$	—	$	—	$	—	$	—	$	—
WTI derivative financial instruments		752		—		—		—		752		—
Total	$	752	$	—	$	—	$	—	$	752	$	—

Schedule of derivative mark-to-market (gains) and losses recognized in the consolidated statement of operations and comprehensive income

	Three Months Ended
	March 31,
	2017		2016
International coal forward contracts	$	—	$	(39)
Domestic coal futures contracts		—		11
WTI derivative financial instruments		2,344		1,990
Net derivative financial instruments loss (gain)	$	2,344	$	1,962