Income Taxes - Deferred Tax Asset/Liability (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets (liabilities)
Research and development tax credits	$ 6,600,000	$ 15,000,000
Net operating losses and credits	4,200,000	10,500,000
Employee benefits	1,100,000	26,000,000
Inventories	200,000	(500,000)
Accrued liabilities	100,000	3,200,000
Deferred Tax Assets, Goodwill and Intangible Assets	(500,000)	(10,800,000)
Accelerated depreciation	(1,600,000)	(34,000,000)
Undistributed foreign earnings	0	(4,400,000)
Other	0	1,100,000
Net deferred income tax assets	10,100,000	6,100,000
Deferred income tax assets (liabilities)
Accelerated depreciation	(45,100,000)	(12,300,000)
Intangibles	(11,400,000)	(2,800,000)
Interest limitation	0	(300,000)
Other	1,300,000	0
Inventories	1,800,000	300,000
Accrued liabilities	1,900,000	0
Net operating losses	5,000,000	0
Research and development tax credits	8,600,000	0
Employee benefits	22,900,000	5,000,000
Net deferred income tax liabilities	(15,000,000)	(10,100,000)
Undistributed earnings of foreign subsidiaries	37,300,000	12,500,000.0
NOLs
Deferred tax asset related to net operating losses	2,600,000
Pre-acquisition built-in loss carryforward	9,300,000
Pre-acquisition built-in carryovers, deferred tax asset	2,000,000
Alternative minimum tax credit carryovers	3,100,000
R&D credit, valuation allowance		3,100,000
State and Local Jurisdiction
NOLs
Net operating losses	44,000,000
Operating loss carryfowards, valuation allowance	400,000	$ 400,000
Research Tax Credit Carryforward | Domestic Tax Authority
NOLs
R & D credits subject to expiration	15,500,000
Research Tax Credit Carryforward | State and Local Jurisdiction
NOLs
R & D credits subject to expiration	$ 6,900,000