Supplemental Executive Retirement Plan (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Reclassifications related to the SERP from accumulated other comprehensive loss to the statement of operations
Amortization of prior service cost	$ 309	$ 207
Amortization of net actuarial loss	52	199
Total amortization of prior service cost and net actuarial loss	361	406
Tax benefit	(126)	(136)
Total, net of tax	235	270
Research and development
Reclassifications related to the SERP from accumulated other comprehensive loss to the statement of operations
Amortization of prior service cost	102	77
Amortization of net actuarial loss	17	74
Selling, general and administrative
Reclassifications related to the SERP from accumulated other comprehensive loss to the statement of operations
Amortization of prior service cost	207	130
Amortization of net actuarial loss	$ 35	$ 125