Accrued liabilities - Accrued Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Payables And Accruals [Abstract]
Accrued salaries and benefits	$ 2,099	$ 2,328
Accrued judgments and settlements	998	3,350
Accrued warranty expense	1,078	955	695	484
Accrued income and other taxes	258	233
Other accrued expenses	1,816	1,974
Accrued liabilities	$ 6,249	$ 8,840