Segment Information (Net Sales By Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net sales	$ 566,852	$ 524,505	$ 535,829
Operating Segments | Performance Materials Segment
Segment Reporting Information [Line Items]
Net sales	111,128	101,478	115,866
Operating Segments | Performance Materials Segment | Filtration
Segment Reporting Information [Line Items]
Net sales	70,430	62,716	71,648
Operating Segments | Performance Materials Segment | Thermal Insulation
Segment Reporting Information [Line Items]
Net sales	27,783	28,311	31,404
Operating Segments | Performance Materials Segment | Life Sciences Filtration
Segment Reporting Information [Line Items]
Net sales	12,915	10,451	12,814
Operating Segments | Technical Nonwovens Segment
Segment Reporting Information [Line Items]
Net sales	155,505	139,133	112,220
Operating Segments | Technical Nonwovens Segment | Industrial Filtration
Segment Reporting Information [Line Items]
Net sales	90,415	113,044	92,721
Operating Segments | Technical Nonwovens Segment | Advanced Materials
Segment Reporting Information [Line Items]
Net sales	65,090	26,089	19,499
Operating Segments | Thermal/Acoustical Metals Segment
Segment Reporting Information [Line Items]
Net sales	174,974	160,932	164,265
Operating Segments | Thermal/Acoustical Metals Segment | Metal parts
Segment Reporting Information [Line Items]
Net sales	156,187	141,117	145,135
Operating Segments | Thermal/Acoustical Metals Segment | Tooling
Segment Reporting Information [Line Items]
Net sales	18,787	19,815	19,130
Operating Segments | Thermal/Acoustical Fibers Segment
Segment Reporting Information [Line Items]
Net sales	149,412	138,747	128,591
Operating Segments | Thermal/Acoustical Fibers Segment | Tooling
Segment Reporting Information [Line Items]
Net sales	5,067	3,152	4,133
Operating Segments | Thermal/Acoustical Fibers Segment | Fiber parts
Segment Reporting Information [Line Items]
Net sales	144,345	135,595	124,458
Operating Segments | Other Products and Services
Segment Reporting Information [Line Items]
Net sales	0	1,671	19,682
Operating Segments | Other Products and Services | Life Sciences Vital Fluids
Segment Reporting Information [Line Items]
Net sales	0	1,671	19,682
Eliminations and Other
Segment Reporting Information [Line Items]
Net sales	$ (24,167)	$ (17,456)	$ (4,795)