Income Taxes (Summary of the Total Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Tax carryforwards	$ 12,812	$ 8,531
Inventories	4,680	7,027
Accrued expenses and reserves	30,640	28,842
Other employee benefits	14,253	13,264
Asset impairment	21,766	14,536
Other	16,170	14,885
Total deferred tax assets	100,321	87,085
Less: Valuation allowance	11,723	8,521
Deferred tax assets, net of valuation allowance	88,598	78,564
Deferred tax liabilities
Depreciation and depletion	42,679	43,111
Accrued pension benefits	3,610	858
Unremitted foreign earnings	296	223
Total deferred tax liabilities	46,585	44,192
Net deferred asset	$ 42,013	$ 34,372