Derivatives (Tables)

6 Months Ended

Jun. 30, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Assets and Liabilities at Fair Value

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

(dollars in thousands)		Fair Value of Derivative Assets
	Balance Sheet Location	June 30, 2018		December 31, 2017
Cash flow hedges:
Interest rate swap	Prepaid and other current assets	$	1,098	$	—
Interest rate swap	Other assets	1,171		646
Natural gas contracts	Prepaid and other current assets	90		—
Total designated		2,359		646
Total derivative assets		$	2,359	$	646
		Fair Value of Derivative Liabilities
		June 30, 2018		December 31, 2017
Cash flow hedges:
Interest rate swap	Derivative liability	$	—	$	213
Natural gas contracts	Derivative liability	—		220
Natural gas contracts	Other long-term liabilities	25		7
Total designated		25		440
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		$	25	$	716

Schedule of Notional Amounts of Outstanding Derivative Positions

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

		Notional Amounts
Derivative Types	Unit of Measure	June 30, 2018		December 31, 2017
Natural gas contracts	Millions of British Thermal Units (MMBTUs)	2,740,000		2,480,000
Interest rate swap	Thousands of U.S. dollars	$	220,000	$	220,000

Schedule of Derivative Instruments

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

	Three months ended June 30,						Six months ended June 30,
(dollars in thousands)	2018			2017			2018			2017
Natural gas contracts	$	(36	)	$	182		$	(234	)	$	298
Interest rate swap	(3		)	(510		)	(181		)	(1,110		)
Total	$	(39	)	$	(328	)	$	(415	)	$	(812	)

Summary of the Gain (Loss) Recognized in the Statement of Operations

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

		Three months ended June 30,						Six months ended June 30,
(dollars in thousands)	Location	2018			2017			2018			2017
Cash flow hedges:
Effective portion of derivative gain (loss) recognized into OCI:
Natural gas contracts	OCI	$	123		$	(239	)	$	334		$	(709	)
Interest rate swap	OCI	480			(619		)	1,733			(415		)
Total		$	603		$	(858	)	$	2,067		$	(1,124	)
Effective portion of derivative gain (loss) reclassified from accumulated OCI to current earnings:
Natural gas contracts	Cost of Sales	$	(36	)	$	90		$	(234	)	$	157
Interest rate swap	Interest expense	40			(472		)	(103		)	(1,057		)
Total		$	4		$	(382	)	$	(337	)	$	(900	)
Derivatives not designated as hedging instruments:
Gain (loss) recognized in current earnings:
Natural gas contracts	Other income (expense)	$	—		$	(236	)	$	—		$	(819	)
Total		$	—		$	(236	)	$	—		$	(819	)