Income Taxes (Deferred Taxes) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Net operating loss carryforward and federal credits	$ 36,624	$ 34,401
Capital and operating leases	2,841	1,742
Post-retirement employee benefits	6,470	62,823
Employee benefits other than post-retirement	16,667	18,010
Inventory reserve	3,050	3,181
Deferred revenue	8,903	10,770
Other	1,262	458
Deferred tax assets	75,817	131,385
Deferred tax liabilities:
Accelerated depreciation	(155,769)	(147,282)
Partnership items	(9,466)	(9,418)
State taxes	(6,265)	(1,724)
Valuation allowance against deferred tax assets	(229)	(229)
Deferred tax liabilities	171,729	158,653
Net deferred tax (liability)	$ (95,912)	$ (27,268)