Industry Segments and Geographic Information (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Financial Information by Geographic Area [Line Items]
Revenues	$ 845,275	$ 872,678	$ 878,877
Identifiable assets	1,203,310	1,299,628	1,347,599
Eliminations [Member]
Financial Information by Geographic Area [Line Items]
Transfers between geographic areas	(322)	(254)	(1,472)
Identifiable assets		(300)	(30)
US [Member]
Financial Information by Geographic Area [Line Items]
Revenues	671,926	735,400	751,101
Identifiable assets	994,151	1,125,512	1,197,512
Canada and Mexico [Member]
Financial Information by Geographic Area [Line Items]
Revenues	49,314	32,645	37,984
Identifiable assets	62,558	35,274	32,811
South America [Member]
Financial Information by Geographic Area [Line Items]
Revenues	28,765	19,802	17,372
Identifiable assets	43,295	47,710	41,556
Europe [Member]
Financial Information by Geographic Area [Line Items]
Revenues	75,033	71,356	68,015
Transfers between geographic areas	322	254	1,472
Identifiable assets	78,974	67,383	59,633
Africa [Member]
Financial Information by Geographic Area [Line Items]
Revenues	13,877	10,194	2,477
Identifiable assets	11,653	10,862	5,468
Asia and other [Member]
Financial Information by Geographic Area [Line Items]
Revenues	6,360	3,281	1,928
Identifiable assets	$ 12,679	$ 13,187	$ 10,649