Stock Based Compensation - Summary of Stock Based Compensation Expense (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock based compensation	$ 3,838,000	$ 3,045,000	$ 1,224,000
Cost of Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock based compensation	351,000	236,000	91,000
Service, rental and maintenance [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock based compensation	108,000	131,000	66,000
Selling and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock based compensation	544,000	336,000	258,000
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock based compensation	$ 2,835,000	$ 2,342,000	$ 809,000