Accumulated Other Comprehensive Loss (Schedule of Reclassifications Out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes		$ (3,639)	$ 5,005	$ 23,225	$ (19,630)
Income tax provision (benefit)		1,764	(2,389)	(5,668)	(7,505)
Net income (loss)		(1,875)	2,616	17,557	(27,135)
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	[1]	(114)	(142)	(378)	(142)
Reclassifications Out of Accumulated Other Comprehensive Income (Loss) | Defined Benefit Plan Items
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior-service cost	[2]	(228)	(227)	(684)	(227)
Income (loss) before income taxes		(228)	(227)	(684)	(227)
Income tax provision (benefit)		60	85	180	85
Net income (loss)		(168)	$ (142)	(504)	$ (142)
Reclassifications Out of Accumulated Other Comprehensive Income (Loss) | Cash Flow Hedges
Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income [Line Items]
Interest payments	[3]	73		171
Income (loss) before income taxes		73		171
Income tax provision (benefit)		(19)		(45)
Net income (loss)		$ 54		$ 126

[1] Amounts in parentheses indicate credits to profit/loss

[2] This accumulated other comprehensive loss component is included in the computation of net periodic benefit cost (see Note 6).

[3]