Goodwill and Intangible Assets - Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Total Goodwill	$ 153,463	$ 82,744
Total intangibles	125,799	86,653
Accumulated amortization	(32,185)	(27,794)
Net intangibles	93,614	58,859
Composite Fibers [Member]
Finite-Lived Intangible Assets [Line Items]
Total Goodwill	79,024	82,744
Composite Fibers [Member] \| Technology and Related [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangibles	38,813	40,686
Composite Fibers [Member] \| Tradename Nonamortizing
Finite-Lived Intangible Assets [Line Items]
Total intangibles	4,556	4,773
Composite Fibers [Member] \| Customer Relationships and Related [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangibles	35,029	36,705
Advanced Airlaid Materials [Member]
Finite-Lived Intangible Assets [Line Items]
Total Goodwill	74,439
Advanced Airlaid Materials [Member] \| Tradename [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangibles	4,534
Advanced Airlaid Materials [Member] \| Technology and Related [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangibles	18,014	1,488
Advanced Airlaid Materials [Member] \| Customer Relationships and Related [Member]
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 24,853	$ 3,001

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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