Property and Equipment - Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 11,807	$ 10,642
Less: Accumulated depreciation and amortization	(8,742)	(6,968)
Property and Equipment, net	3,065	3,674
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	5 years
Property and Equipment, gross	3,333	2,854
Prototype Systems [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	2 years
Property and Equipment, gross	1,893	1,893
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	3 years
Property and Equipment, gross	1,325	651
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	5 years
Property and Equipment, gross	543	517
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	Various
Property and Equipment, gross	4,713	4,713
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross		$ 14