Warranty Contracts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Warranty Contracts [Line Items]
Deferred warranty revenue beginning balance	$ 9,141	$ 4,081	$ 3,094
Warranty revenue deferred	17,185	14,681	7,540
Warranty revenue recognized	(14,412)	(9,621)	(6,553)
Deferred warranty revenue ending balance	11,914	9,141	4,081
Warranty Costs Incurred	12,620	9,262	6,392
Product Warranty Period	1 year
Materials [Member]
Warranty Contracts [Line Items]
Warranty Costs Incurred	5,958	4,441	2,672
Labor And Overhead [Member]
Warranty Contracts [Line Items]
Warranty Costs Incurred	$ 6,662	$ 4,821	$ 3,720