Accumulated Other Comprehensive (Loss) Income - Schedule of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax
Total accumulated other comprehensive (loss) income, beginning of period			$ (91,726)
Total accumulated other comprehensive (loss) income, end of period	$ (90,908)		(90,908)
Changes in Fair Market Value of Hedges
Changes in AOCI, Gross
Gross, beginning of the period	(4,239)	$ 1,036	659	$ 1,316
Gross, gain (loss) recognized in OCI	525	(529)	(4,647)	(181)
Gross, gain (loss) reclassified from AOCI to Earnings	656	(426)	930	(1,054)
Gross, ending balance	(3,058)	81	(3,058)	81
Changes in AOCI, Income tax benefit (expense)
Income tax benefit (expense), beginning of period	978	(234)	(150)	(298)
Income tax benefit (expense), gain (loss) recognized in OCI	(122)	119	1,059	41
Income tax benefit (expense), gain (loss) reclassified from AOCI to Earnings	(150)	96	(203)	238
Income tax benefit (expense), ending of period	706	(19)	706	(19)
AOCI Attributable to Parent, Net of Tax
Total accumulated other comprehensive (loss) income, beginning of period	(3,261)	802	509	1,018
Gain (loss) recognized in OCI, net	403	(410)	(3,588)	(140)
Gain (loss) reclassified from AOCI to Earnings, net	506	(330)	727	(816)
Total accumulated other comprehensive (loss) income, end of period	(2,352)	62	(2,352)	62
Changes in Unrealized Pension Cost
Changes in AOCI, Gross
Gross, beginning of the period	(120,906)	(129,810)	(124,140)	(132,454)
Gross, gain (loss) recognized in OCI	0	0	0	0
Gross, gain (loss) reclassified from AOCI to Earnings	1,606	1,313	4,840	3,957
Gross, ending balance	(119,300)	(128,497)	(119,300)	(128,497)
Changes in AOCI, Income tax benefit (expense)
Income tax benefit (expense), beginning of period	33,278	35,297	34,018	35,893
Income tax benefit (expense), gain (loss) recognized in OCI	0	0	0	0
Income tax benefit (expense), gain (loss) reclassified from AOCI to Earnings	(367)	(296)	(1,107)	(892)
Income tax benefit (expense), ending of period	32,911	35,001	32,911	35,001
AOCI Attributable to Parent, Net of Tax
Total accumulated other comprehensive (loss) income, beginning of period	(87,628)	(94,513)	(90,122)	(96,561)
Gain (loss) recognized in OCI, net	0	0	0	0
Gain (loss) reclassified from AOCI to Earnings, net	1,239	1,017	3,733	3,065
Total accumulated other comprehensive (loss) income, end of period	(86,389)	(93,496)	(86,389)	(93,496)
Cumulative Translation Adjustment
Changes in AOCI, Gross
Gross, beginning of the period	(2,266)	(2,287)	(2,211)	(2,291)
Gross, gain (loss) recognized in OCI	99	(89)	44	(85)
Gross, gain (loss) reclassified from AOCI to Earnings	0	0	0	0
Gross, ending balance	(2,167)	(2,376)	(2,167)	(2,376)
Changes in AOCI, Income tax benefit (expense)
Income tax benefit (expense), beginning of period	0	95	98	95
Income tax benefit (expense), gain (loss) recognized in OCI	0	(3)	(98)	(3)
Income tax benefit (expense), gain (loss) reclassified from AOCI to Earnings	0	0	0	0
Income tax benefit (expense), ending of period	0	92	0	92
AOCI Attributable to Parent, Net of Tax
Total accumulated other comprehensive (loss) income, beginning of period	(2,266)	(2,192)	(2,113)	(2,196)
Gain (loss) recognized in OCI, net	99	(92)	(54)	(88)
Gain (loss) reclassified from AOCI to Earnings, net	0	0	0	0
Total accumulated other comprehensive (loss) income, end of period	(2,167)	(2,284)	(2,167)	(2,284)
Accumulated Other Comprehensive Earnings/(Loss)
AOCI Attributable to Parent, Net of Tax
Total accumulated other comprehensive (loss) income, beginning of period	(93,155)	(95,903)	(91,726)	(97,739)
Gain (loss) recognized in OCI, net	502	(502)	(3,642)	(228)
Gain (loss) reclassified from AOCI to Earnings, net	1,745	687	4,460	2,249
Total accumulated other comprehensive (loss) income, end of period	$ (90,908)	$ (95,718)	$ (90,908)	$ (95,718)