Commitments - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Contractual Obligation [Line Items]
Agreement for purchase of equipment	$ 2,525,000	$ 1,693,000
Laboratory And Computer Equipment [Member] | Wells Fargo Equipment Finance [Member]
Contractual Obligation [Line Items]
Agreement for purchase of equipment	1,400,000
Lease term period	60 months
Buyout option	1
Interest rate	4.08%
Other Lease Agreement [Member] | Computer Equipment and Computer Software [Member]
Contractual Obligation [Line Items]
Agreement for purchase of equipment	1,100,000
Buyout option	$ 1
Minimum [Member] | Other Lease Agreement [Member] | Computer Equipment and Computer Software [Member]
Contractual Obligation [Line Items]
Lease term period	36 months
Interest rate	4.25%
Maximum [Member] | Other Lease Agreement [Member] | Computer Equipment and Computer Software [Member]
Contractual Obligation [Line Items]
Interest rate	13.50%