Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of available-for-sale investments measured at fair value on a recurring basis, categorized by level of inputs used in the valuation

Available-for-sale investments measured at fair value on a recurring basis, categorized by the level of inputs used in the valuation, were as follows:

	Available-for-Sale Investment at Fair Value as of December 31, 2020
(Dollars in thousands)	Level 1		Level 2		Level 3		Total
Pension surplus investment(1)	$	6,706	$	2,400	$	—	$	9,106

(1) This balance was invested in funds comprised of short-term cash and fixed income securities, and was recorded in the “Other long-term assets” line item in the condensed consolidated statements of financial position. As of December 31, 2020, the fair value of this investment approximated its carrying value.

Schedule of derivative instruments measured at fair value on a recurring basis, categorized by the level of inputs used in the valuation

Derivative instruments measured at fair value on a recurring basis, categorized by the level of inputs used in the valuation, include:

	Derivative Instruments at Fair Value as of December 31, 2020
(Dollars in thousands)	Level 1		Level 2		Level 3		Total(1)
Foreign currency contracts	$	—	$	(130)	$	—	$	(130)
Copper derivative contracts	$	—	$	4,785	$	—	$	4,785
Interest rate swap contract	$	—	$	—	$	—	$	—

	Derivative Instruments at Fair Value as of December 31, 2019
(Dollars in thousands)	Level 1		Level 2		Level 3		Total(1)
Foreign currency contracts	$	—	$	(6)	$	—	$	(6)
Copper derivative contracts	$	—	$	1,147	$	—	$	1,147
Interest rate swap contract	$	—	$	(1,254)	$	—	$	(1,254)

(1) All balances were recorded in the “Other current assets” or “Other accrued liabilities” line items in the consolidated statements of financial position, except the 2019 interest rate swap balance, which was recorded in the “Other long-term liabilities” line item.