Industry Segments and Geographic Information (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
US [Member]
Financial Information by Geographic Area [Line Items]
Revenues	$ 625,885	$ 671,926	$ 735,400
Identifiable assets	913,080	994,151	1,125,512
Canada and Mexico [Member]
Financial Information by Geographic Area [Line Items]
Revenues	85,133	49,314	32,645
Identifiable assets	116,059	62,558	35,274
South America [Member]
Financial Information by Geographic Area [Line Items]
Revenues	42,482	28,765	19,802
Identifiable assets	51,858	43,295	47,710
Europe [Member]
Financial Information by Geographic Area [Line Items]
Revenues	92,882	75,033	71,356
Transfers between geographic areas	172	322	254
Identifiable assets	135,219	78,974	67,383
Africa [Member]
Financial Information by Geographic Area [Line Items]
Revenues	20,194	13,877	10,194
Identifiable assets	13,700	11,653	10,862
Asia and other [Member]
Financial Information by Geographic Area [Line Items]
Revenues	14,255	6,360	3,281
Identifiable assets	31,902	12,679	13,187
Eliminations [Member]
Financial Information by Geographic Area [Line Items]
Transfers between geographic areas	(172)	(322)	(254)
Identifiable assets	$ 0	$ 0	$ (300)