Derivatives Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2015

Derivative [Line Items]

Schedule of offsetting and balance sheet presentation

		September 30, 2015
		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		$	11,149	$	—	$	—	$	—	$	11,149	$	—
International coal put options			4,783		—		—		—		4,783		—
WTI derivative financial instruments			—		(8,351)		(4,246)		4,246		(4,246)		(4,106)
U.S. On-Highway Diesel derivative
	financial instruments		—		(4,429)		(4,429)		4,429		(4,429)		—
Total		$	15,932	$	(12,780)	$	(8,675)	$	8,675	$	7,258	$	(4,106)

	December 31, 2014
	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	$	20,861	$	(129)	$	(129)	$	129	$	20,732	$	—
WTI derivative financial instruments		—		(7,228)		(3,620)		3,620		(3,620)		(3,608)
Total	$	20,861	$	(7,357)	$	(3,749)	$	3,749	$	17,111	$	(3,608)

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

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2015		2014		2015		2014
International coal forward contracts	$	(1,153)	$	(3,989)	$	(5,999)	$	(18,071)
International coal put options		(4,039)		—		5,155		—
Domestic coal futures contracts		(564)		2,946		4,095		1,958
WTI derivative financial instruments		11,500		526		8,875		60
U.S. On-Highway Diesel derivative financial instruments		4,491		—		5,656		—
Net derivative financial instruments loss (gain)	$	10,235	$	(515)	$	17,781	$	(16,052)

Coal Contracts

Derivative [Line Items]

Schedule of derivative financial instruments

	2015		2016		Total
International Coal Forward Contracts
Notional amount (tons)		172		132		304
Net asset position	$	4,117	$	7,032	$	11,149
Weighted-average per ton	$	99.53	$	100.13	$	99.90
International Coal Put Options
Notional amount (tons)		—		2,480		2,480
Net asset position	$	—	$	4,783	$	4,783
Weighted-average per ton	$	—	$	44.75	$	44.75
Domestic Coal Futures Contracts
Notional amount (tons)		360		120		480
Weighted-average per ton	$	13.10	$	14.70	$	13.50

WTI derivative financial instruments

Derivative [Line Items]

Schedule of derivative financial instruments

	Floor			Ceiling			Swaps
Settlement Period	Notional Amount	Weighted-Average per Barrel		Notional Amount	Weighted-Average per Barrel		Notional Amount	Weighted-Average per Barrel
	(barrels in thousands)			(barrels in thousands)			(barrels in thousands)
2015 swap positions (1)	—	$	—	—	$	—	173	$	53.20
2016 collar positions (2)	342	$	53.94	342	$	72.88	—	$	—
2016 swap positions (2)	—	$	—	—	$	—	342	$	63.39
Total	342	$	53.94	342	$	72.88	515	$	59.96

• Represents 100% of expected diesel consumption for the fourth quarter of 2015.
• Represents 50% of expected diesel consumption for 2016.

U.S. on-highway diesel contracts

Derivative [Line Items]

Schedule of derivative financial instruments

	Swaps
Settlement Period	Notional Amount	Weighted-Average per Gallon
	(gallons in thousands)
2015 swap positions	2,650	$	3.10
2016 swap positions	6,400	$	3.18
Total	9,050	$	3.16