Deferred Revenue (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Customer	Dec. 31, 2012
Deferred Revenue (Textual)
Deferred fees	$ 2,920	$ 2,725
Prepayments from future license fees [Member]
Deferred Revenue (Textual)
Deferred fees	2,000	2,100
Number of customer	3
Deferred engineering development fees [Member]
Deferred Revenue (Textual)
Deferred fees	$ 900	$ 600
Number of customer	13