Taxes on Income, Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets [Abstract]
Allowance for doubtful accounts	$ 1,793,000	$ 1,758,000
Inventory	13,496,000	13,401,000
Insurance accruals	4,864,000	4,397,000
Deferred compensation	6,040,000	1,109,000
Unrealized loss on defined benefit plans	15,929,000	10,253,000
Goodwill and other intangibles	44,487,000	0
Operating loss carryforwards	82,186,000	143,181,000
Pension benefits	7,444,000	6,825,000
Other	5,480,000	7,392,000
Deferred tax assets, gross	181,719,000	188,316,000
Valuation allowances	(18,025,000)	(20,525,000)
Deferred tax assets, net of valuation allowance	163,694,000	167,791,000
Deferred tax liabilities [Abstract]
Property	(678,916,000)	(620,891,000)
Deferred state taxes	(74,468,000)	(63,640,000)
Goodwill and other intangibles	0	(54,844,000)
Other	(17,154,000)	(16,620,000)
Deferred tax liabilities	(770,538,000)	(755,995,000)
Net deferred tax liabilities	(606,844,000)	(588,204,000)
Operating Loss Carryforward [Abstract]
Deferred tax assets	53,498,000
State operating loss deferred tax assets	23,482,000	17,282,000
Operating loss carryforwards, net of valuation allowance	$ 12,819,000	$ 11,760,000
Expiration dates, operating loss carryforwards	Dec. 31, 2037
Unrecognized tax benefits including interest and penalties	$ 971,000
Amount that would impact the effective tax rate, if recognized	790,000
Canada [Member]
Operating Loss Carryforward [Abstract]
Operating loss carryforwards	$ 5,206,000
Expiration dates, operating loss carryforwards	Dec. 31, 2040
Internal Revenue Service (IRS) [Member]
Open Tax Year [Abstract]
Years open to audit under the statute of limitations	2017 2018 2019
State and Local Jurisdiction [Member]
Open Tax Year [Abstract]
Years open to audit under the statute of limitations	2014 2015 2016 2017 2018 2019