Stockholders' Equity and Stock Based Compensation - Schedule of Stock Based Compensation Expense for Awards Under Equity Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	$ 700	$ 394	$ 2,067	$ 1,497
General and administrative [Member] | Board Of Directors [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	107	93	321	278
Long-term Incentive Plan [Member] | Cost of revenue [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	57	33	164	101
Long-term Incentive Plan [Member] | Service, rental and maintenance [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	61	29	177	86
Long-term Incentive Plan [Member] | Selling and marketing [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	75	16	198	118
Long-term Incentive Plan [Member] | General and administrative [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	391	223	1,198	914
Employee Stock Purchase Plan [Member] | General and administrative [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	$ 9	$ 0	$ 9	$ 0