Fair Value Measurements and Fair Value of Financial Instruments - Summary of Changes in Estimated Fair Value of Warrants Liabilities and Embedded Derivative Liability (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Embedded Derivative Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0	$ 18
Issuance of common stock warrant	0
De-recognition of embedded derivative upon conversion of convertible notes		(18)
Change in fair value	0	0
Ending balance	0	0
Common Stock [Member] | Warrants [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	42	5
Issuance of common stock warrant	(41)
De-recognition of embedded derivative upon conversion of convertible notes		0
Change in fair value	(1)	37
Ending balance	0	42
Series A and B Convertible Preferred Stock [Member] | Warrants [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	91	36
Issuance of common stock warrant	0
De-recognition of embedded derivative upon conversion of convertible notes		0
Change in fair value	470	55
Ending balance	$ 561	$ 91