Fair Value Measurements - Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012 Fair value, recurring basis [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Preferred stock warrant liability [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Preferred stock warrant liability [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Significant Other Observable Inputs (Level 2) [Member] Preferred stock warrant liability [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Fair value, recurring basis [Member] Significant Unobservable Inputs (Level 3) [Member] Preferred stock warrant liability [Member]
Liabilities:
Total liabilities	$ 0	$ 56,000	$ 56,000					$ 56,000	$ 56,000