Segment Information (Net Sales By Segment) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 535,829	$ 397,969	$ 378,924
Performance materials segment
Segment Reporting Information [Line Items]
Net sales	115,866	112,001	118,035
Industrial Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	112,220	0	0
Thermal acoustical fibers segments
Segment Reporting Information [Line Items]
Net sales	164,265	158,406	153,921
Thermal and Acoustical Fibers [Member]
Segment Reporting Information [Line Items]
Net sales	128,591	114,320	94,436
Other Products and Services Segment [Member]
Segment Reporting Information [Line Items]
Net sales	19,682	17,175	16,853
Industrial Filtration [Member] | Performance Materials [Member]
Segment Reporting Information [Line Items]
Net sales	71,648	64,752	68,379
Industrial Filtration [Member] | Industrial Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	112,220	0	0
Industrial Thermal Insulation [Member] | Performance Materials [Member]
Segment Reporting Information [Line Items]
Net sales	31,404	36,929	38,449
Life Sciences Filtration [Member] | Performance Materials [Member]
Segment Reporting Information [Line Items]
Net sales	12,814	10,320	11,207
Metal Parts [Member] | Thermal and Acoustical Metals [Member]
Segment Reporting Information [Line Items]
Net sales	145,135	135,833	136,276
Tooling [Member] | Thermal and Acoustical Metals [Member]
Segment Reporting Information [Line Items]
Net sales	19,130	22,573	17,645
Tooling [Member] | Thermal and Acoustical Fibers [Member]
Segment Reporting Information [Line Items]
Net sales	4,133	8,444	917
Fiber Parts [Member] | Thermal and Acoustical Fibers [Member]
Segment Reporting Information [Line Items]
Net sales	124,458	105,876	93,519
Life Sciences Vital Fluids [Member] | Other Products and Services Segment [Member]
Segment Reporting Information [Line Items]
Net sales	19,682	17,175	16,853
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Eliminations and Other	$ 4,795	$ 3,933	$ 4,321