Segment Reporting (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2013	Sep. 28, 2012	Sep. 27, 2013	Sep. 28, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales to external customers	$ 275,434	$ 290,601	$ 880,744	$ 969,319
Intersegment sales	1,189	1,483	4,332	4,823
Operating profit (loss)	5,982	13,389	28,894	35,718
Assets	805,998	818,359	805,998	818,359	814,917
Subtotal [Member]
Segment Reporting Information [Line Items]
Sales to external customers	275,434	290,601	880,744	969,240
Intersegment sales	1,189	1,483	4,332	4,823
Operating profit (loss)	7,435	15,236	32,814	41,532
Assets	752,742	781,896	752,742	781,896
Advanced Material Technologies [Member]
Segment Reporting Information [Line Items]
Sales to external customers	176,294	190,508	566,158	654,245
Intersegment sales	523	520	2,048	1,691
Operating profit (loss)	4,800	9,212	12,694	22,011
Assets	319,593	366,190	319,593	366,190
Performance Alloys [Member]
Segment Reporting Information [Line Items]
Sales to external customers	69,578	68,700	218,435	216,434
Intersegment sales	443	599	1,484	1,968
Operating profit (loss)	4,520	5,404	18,654	18,349
Assets	267,232	257,825	267,232	257,825
Beryllium and Composites [Member]
Segment Reporting Information [Line Items]
Sales to external customers	13,685	14,418	42,194	43,102
Intersegment sales	67	245	200	574
Operating profit (loss)	(3,306)	(515)	(3,780)	(3,823)
Assets	142,183	134,787	142,183	134,787
Technical Materials [Member]
Segment Reporting Information [Line Items]
Sales to external customers	15,877	16,975	53,957	55,459
Intersegment sales	156	119	600	590
Operating profit (loss)	1,421	1,135	5,246	4,995
Assets	23,734	23,094	23,734	23,094
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)	(1,453)	(1,847)	(3,920)	(5,814)
Assets	$ 53,256	$ 36,463	$ 53,256	$ 36,463