Inventories: (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Inventory Disclosure [Abstract]
Raw material	$ 21,924	$ 25,227
Work in process	3,861	2,901
Finished goods	11,505	12,295
Total	$ 37,290	$ 40,423	[1]

[1] December 31, 2011 balances were derived from audited consolidated financial statements.