Segment Reporting (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2013	Jun. 29, 2012	Jun. 28, 2013	Jun. 29, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales to external customers	$ 306,141	$ 325,088	$ 605,310	$ 678,718
Intersegment sales	1,665	1,514	3,143	3,340
Operating profit (loss)	13,390	12,445	22,912	22,329
Assets	803,497	800,114	803,497	800,114	814,917
Advanced Material Technologies [Member]
Segment Reporting Information [Line Items]
Sales to external customers	196,011	221,931	389,864	463,737
Intersegment sales	777	506	1,525	1,171
Operating profit (loss)	4,543	7,514	7,894	12,799
Assets	325,746	353,824	325,746	353,824
Performance Alloys [Member]
Segment Reporting Information [Line Items]
Sales to external customers	74,335	72,506	148,857	147,734
Intersegment sales	611	672	1,041	1,369
Operating profit (loss)	6,898	6,685	14,134	12,945
Assets	266,561	248,086	266,561	248,086
Beryllium and Composites [Member]
Segment Reporting Information [Line Items]
Sales to external customers	16,187	12,567	28,509	28,684
Intersegment sales	63	129	133	329
Operating profit (loss)	822	(2,017)	(474)	(3,308)
Assets	141,509	130,309	141,509	130,309
Technical Materials [Member]
Segment Reporting Information [Line Items]
Sales to external customers	19,608	18,084	38,080	38,484
Intersegment sales	214	207	444	471
Operating profit (loss)	2,389	1,967	3,825	3,860
Assets	24,530	23,824	24,530	23,824
Subtotal [Member]
Segment Reporting Information [Line Items]
Sales to external customers	306,141	325,088	605,310	678,639
Intersegment sales	1,665	1,514	3,143	3,340
Operating profit (loss)	14,652	14,149	25,379	26,296
Assets	758,346	756,043	758,346	756,043
All Other [Member]
Segment Reporting Information [Line Items]
Sales to external customers	0	0	0	79
Intersegment sales	0	0	0	0
Operating profit (loss)	(1,262)	(1,704)	(2,467)	(3,967)
Assets	$ 45,151	$ 44,071	$ 45,151	$ 44,071