Income Taxes (Deferred Taxes) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
deferred tax asset, warrant remeasurement	$ 17,174	$ 7,314
Deferred tax assets:
Net operating loss carryforward and federal credits	40,467	55,760
Post-retirement employee benefits	6,355	13,777
Employee benefits other than post-retirement	9,435	8,751
Inventory reserve	2,055	2,374
Deferred revenue	5,132	4,389
Other	9,309	5,333
Deferred tax assets	98,997	97,698
Deferred Tax Assets, Capital and Operating Leases	9,070	0
Deferred tax liabilities:
Accelerated depreciation	(192,651)	(189,719)
Partnership items	(6,088)	(5,850)
State taxes	(12,355)	(14,474)
Valuation allowance against deferred tax assets	(1,412)	(278)
Deferred tax liabilities	226,473	210,941
Net deferred tax (liability)	(127,476)	(113,243)
Deferred Tax Liabilities, Leasing Arrangements	(9,051)	0
Deferred Tax Liabilities, Goodwill	$ (4,916)	$ (620)