Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Accrued Expenses and Other Current Liabilities
Payroll and related costs	$ 2,948		$ 1,429
Employee benefits	3,122		2,731
Accrued warranty	3,881	3,568	3,628	4,173	3,965	4,188
Other	3,701		2,541
Accrued expenses and other current liabilities	$ 13,652		$ 10,329