Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Accrued compensated absences	$ 1,565,000	$ 3,557,000
Pensions	14,964,000	31,071,000
Post-retirement benefits	12,817,000	36,563,000
Federal net operating loss carry forward	14,177,000	30,528,000
State net operating loss carry forward	15,510,000	14,590,000
Cellulosic biofuel credit carry forward	12,830,000	12,830,000
Other	14,035,000	16,313,000
Gross deferred tax asset	85,898,000	145,452,000
Less valuation allowance	(20,885,000)	(102,000)
Net deferred tax assets	65,013,000	145,350,000
Deferred tax liabilities:
Property, plant, and equipment	(36,042,000)	(100,953,000)
Other	(18,619,000)	(19,198,000)
Gross deferred tax liability	(54,661,000)	(120,151,000)
Net deferred tax asset	10,352,000	25,199,000
Total deferred tax assets (liabilities)
Net current deferred tax (liabilities) assets	(10,118,000)	5,703,000
Net noncurrent deferred tax assets	20,470,000	19,496,000
Net deferred tax asset	10,352,000	25,199,000
Liability for unrecognized tax benefits
Balance at the beginning of the period	1,049,000	1,362,000	857,000
Increases related to tax positions in prior years	788,000	49,000	722,000
Decreases related to tax positions in prior years			(6,000)
Expiration of statute of limitations	(46,000)	(362,000)	(211,000)
Balance at the end of the period	1,791,000	1,049,000	1,362,000
Decrease in interest and penalties related to tax expiration of the statute of limitations, maximum	100,000	100,000
Liabilities for potential penalties and interest for unrecognized tax benefits	500,000	500,000
Liability for uncertain tax positions	2,300,000	1,500,000
Current liability for uncertain tax positions	900,000	400,000
Noncurrent liability for uncertain tax positions	1,400,000	1,100,000
Federal
Tax credit carryovers
Tax credit carryovers	12,900,000
Valuation allowance related to tax credit carryover	8,000,000
State
Tax credit carryovers
Tax credit carryovers	10,800,000
Valuation allowance related to tax credit carryover	$ 12,900,000