Segment Geographic and Market Information (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Net sales by source
Net sales of tangible goods	$ 709,310	[1]	$ 628,839	[1]	$ 522,003	[1]
Services revenues	206,299	[1]	166,750	[1]	136,601	[1]
Freight revenue	28,187	[1]	30,688	[1]	28,881	[1]
Total	943,796	[1]	826,277	[1]	687,485	[1]
Cost of sales
Cost of tangible goods sold	512,489	[1]	461,177	[1]	383,752	[1]
Cost of services rendered	157,037	[1]	126,056	[1]	96,148	[1]
Cost associated with freight revenue	21,953	[1]	24,859	[1]	23,294	[1]
Total	$ 691,479	[1]	$ 612,092	[1]	$ 503,194	[1]

[1] Restated