Noncontrolling Interest (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Noncontrolling Interest (Textual) [Abstract]
Remaining noncontrolling interest acquired	$ 5,702	[1]	$ (2,701)	[1]	$ 5,528	[1]
Volclay South Africa (Proprietary) Limited [Member]
Noncontrolling Interest (Textual) [Abstract]
Remaining noncontrolling interest acquired	$ 5,600
Vengawave (Proprietary) Limited [Member]
Noncontrolling Interest (Textual) [Abstract]
Percentage of interest sold (in hundredths)	26.00%

[1] Restated