Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net (loss) income	$ (3,803)	$ (13,527)	$ (6,734)	$ 32,629	$ (17,330)	$ 25,893
Other comprehensive income (loss):
Adjustment to pension liability	732		686		1,465	1,377
Tax expense	(183)		(169)		(366)	(342)
Adjustment to pension liability, net of tax	549				1,099
Adjustment to pension liability, net of tax	549		517		1,099	1,035
Foreign currency translation adjustment, net of tax	377		(805)		349	(959)
Adoption of ASU 2018-2					(11,355)	0
Total other comprehensive (loss) income, net of tax	926		(288)		(9,907)	76
Comprehensive (loss) income	(2,877)		(7,022)		(27,237)	25,969
Accumulated other comprehensive income
Less: Earnings attributable to participating securities					0	3,059
Changes in other comprehensive loss by component
Balance	(32,000)	(19,184)	(636)	(34,635)	(19,184)	(34,635)
Other comprehensive income (loss), net of tax, before reclassifications					349	(959)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax, to other, net, on the condensed consolidated statements of comprehensive (loss) income					1,099	1,035
Adoption of ASU 2018-02					(11,355)	0
Total other comprehensive (loss) income, net of tax	926		(288)		(9,907)	76
Balance	(34,642)	(32,000)	(7,268)	(636)	(34,642)	(7,268)
Total
Changes in other comprehensive loss by component
Balance	(57,316)	(46,483)	(43,939)	(44,303)	(46,483)	(44,303)
Balance	(56,390)	(57,316)	(44,227)	(43,939)	(56,390)	(44,227)
Defined Benefit Pension Items
Other comprehensive income (loss):
Adoption of ASU 2018-2	(11,355)
Total other comprehensive (loss) income, net of tax					(10,256)	1,035
Changes in other comprehensive loss by component
Balance		(46,584)		(45,418)	(46,584)	(45,418)
Other comprehensive income (loss), net of tax, before reclassifications					0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax, to other, net, on the condensed consolidated statements of comprehensive (loss) income					1,099	1,035
Adoption of ASU 2018-02	(11,355)
Total other comprehensive (loss) income, net of tax					(10,256)	1,035
Balance	(56,840)		(44,383)		(56,840)	(44,383)
Foreign Currency Items
Other comprehensive income (loss):
Adoption of ASU 2018-2
Total other comprehensive (loss) income, net of tax					349	(959)
Changes in other comprehensive loss by component
Balance		$ 101		$ 1,115	101	1,115
Other comprehensive income (loss), net of tax, before reclassifications					349	(959)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax, to other, net, on the condensed consolidated statements of comprehensive (loss) income					0	0
Adoption of ASU 2018-02
Total other comprehensive (loss) income, net of tax					349	(959)
Balance	$ 450		$ 156		$ 450	$ 156