Inventories (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Changes In the Inventory Reserves
Balance at beginning of period	$ 1,783	$ 1,793
Provisions for (realization of) losses	5	(15)
Write-offs and disposals	(83)	(3)
Balance at end of period	$ 1,705	$ 1,775