Fair Value Measurements - Summary of Changes in Fair Value Financial Instruments (Detail) (Level 3 [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Conversion of preferred stock call option liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 21
Issuance of financial instruments		990
Fair value of call option liability recognized upon issuance of preferred stock
Change in fair value recorded in other income (expense), net	9,560	(290)
Conversion of preferred stock into common stock and reclassification to permanent equity	(9,581)
Ending balance		700
Conversion of preferred stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	474	433
Issuance of financial instruments
Fair value of call option liability recognized upon issuance of preferred stock
Change in fair value recorded in other income (expense), net	2,279
Conversion of preferred stock into common stock and reclassification to permanent equity	(2,753)
Ending balance		$ 433