Stock Based Compensation - Stock Based Compensation Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation	$ 946,000	$ 460,000	$ 2,200,000	$ 902,000
Service, Rental and Maintenance [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation	34,000	6,000	54,000	18,000
Selling and Marketing [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation	18,000	19,000	52,000	53,000
General and Administrative [Member]
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation	$ 894,000	$ 435,000	$ 2,094,000	$ 831,000