Income Taxes - Components of Deferred Taxes and Uncertain Tax Positions (Details 8) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets
Net operating loss and credit carryforwards	$ 4,875	$ 5,736
Accruals	11,159	10,524
Inventories	15,403	12,856
Pensions	11,303	10,670
Valuation allowance	(2,682)	(2,576)
Total deferred tax assets	40,058	37,210
Deferred tax liabilities
Property, plant and equipment	49,272	39,708
Goodwill and other intangible assets	6,108	6,039
U.S. liability on Belgian and German net deferred tax assets	708	829
Total deferred tax liabilities	56,088	46,576
Net deferred tax liability	(16,030)	(9,366)
Uncertain tax liabilities that partially offset net operating losses and credit carryforwards	200	300
Net indirect benefits on uncertain tax liabilities	61	74
Reconciliation of the unrecognized income tax benefits
Balance at beginning of year	1,187	3,435	$ 4,141
Gross decreases for tax positions of prior years			(438)
Gross increases for tax positions of current year	78	75	122
Lapse of statute of limitations	(417)	(500)	(390)
Settlement of uncertain tax positions	(70)	(1,823)
Balance at end of year	778	1,187	$ 3,435
Gross unrecognized tax benefits that would impact effective tax rate	600	1,000
Interest and penalties accrued on current and prior year uncertain tax positions	33
Interest and penalties accrued on prior year uncertain positions		100
Interest and penalties reversed due to the expiration of the statute of limitations	100	100
Interest and penalties reversed due to the settlement of uncertain positions		600
Amount accrued for payment of interest and penalties related to unrecognized tax benefits	300	300
Unrecognized tax benefits that are reasonably possible to be recognized within the next twelve months	100
Accounts payable and accrued liabilities
Deferred tax liabilities
Current deferred tax liability		200
Accrued pension and other liabilities
Reconciliation of the unrecognized income tax benefits
Uncertain tax positions	$ 900	$ 1,300