Derivatives (Tables)

12 Months Ended

Dec. 31, 2017

Derivative Instruments, Gain (Loss) [Line Items]

Fair Values of Derivative Instruments

The following table provides the fair values of our derivative financial instruments for the periods presented:

December 31, (dollars in thousands)		Fair Value of Derivative Assets
	Balance Sheet Location	2017		2016
Cash flow hedges:
Interest rate swap	Other assets	$	646	$	—
Natural gas contracts	Prepaid and other current assets	—		702
Natural gas contracts	Other assets	—		45
Total designated		646		747
Derivatives not designated as hedging instruments:
Natural gas contracts	Prepaid and other current assets	—		732
Natural gas contracts	Other assets	—		29
Total undesignated		—		761
Total derivative assets		$	646	$	1,508

December 31, (dollars in thousands)		Fair Value of Derivative Liabilities
	Balance Sheet Location	2017		2016
Cash flow hedges:
Interest rate swap	Derivative liability	$	213	$	1,928
Interest rate swap	Other long-term liabilities	—		107
Natural gas contracts	Derivative liability	220		—
Natural gas contracts	Other long-term liabilities	7		—
Total designated		440		2,035
Derivatives not designated as hedging instruments:
Natural gas contracts	Derivative liability	264		—
Natural gas contracts	Other long-term liabilities	12		—
Total undesignated		276		—
Total derivative liabilities		$	716	$	2,035

Schedule of Notional Amounts of Outstanding Derivative Positions

The following table presents the notional amount of derivatives on the Consolidated Balance Sheets:

		Notional Amounts
Derivative Types	Unit of Measure	December 31, 2017		December 31, 2016
Natural gas contracts	Millions of British Thermal Units (MMBTUs)	2,480,000		2,590,000
Interest rate swap	Thousands of U.S. dollars	$	220,000	$	220,000
Currency contracts	Thousands of Canadian dollars	C$	—	C$	—

Cash Settlements

The following table presents cash settlements (paid) received related to the below derivatives:

Year ended December 31, (dollars in thousands)	2017			2016			2015
Natural gas contracts	$	(47	)	$	(2,345	)	$	(4,567	)
Interest rate swap	(1,836		)	(2,244		)	—
Total	$	(1,883	)	$	(4,589	)	$	(4,567	)

Summary of the gain (loss) recognized in the Statement of Operations and AOCI

The following table provides a summary of the impacts of derivative gain (loss) on the Consolidated Statements of Operations and other comprehensive income (OCI):

Year ended December 31, (dollars in thousands)	Location	2017			2016			2015
Cash flow hedges:
Effective portion of derivative gain (loss) recognized in OCI:
Natural gas contracts	OCI	$	(1,019	)	$	721		$	(1,909	)
Interest rate swap	OCI	733			(2,056		)	(2,378		)
Total		$	(286	)	$	(1,335	)	$	(4,287	)
Effective portion of derivative gain (loss) reclassified from accumulated OCI to current earnings:
Natural gas contracts	Cost of Sales	$	(45	)	$	(1,129	)	$	(2,131	)
Interest rate swap	Interest expense	(1,735		)	(2,399		)	—
Total		$	(1,780	)	$	(3,528	)	$	(2,131	)
Derivatives not designated as hedging instruments:
Gain (loss) recognized in current earnings:
Currency contracts	Other income (expense)	$	—		$	(245	)	$	(158	)
Natural gas contracts	Other income (expense)	(1,036		)	1,860			218
Total		$	(1,036	)	$	1,615		$	60