Fair Value on Financial Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Fair value of financial assets and liabilities
Total financial assets	$ 46,500		$ 10,268
Total financial liabilities	10,290		5,903
Money Market Funds
Fair value of financial assets and liabilities
Total financial assets	46,500	[1]	10,268	[1]
Warrant Liability
Fair value of financial assets and liabilities
Total financial liabilities	10,290		5,903
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value of financial assets and liabilities
Total financial assets	46,500		10,268
Total financial liabilities	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
Fair value of financial assets and liabilities
Total financial assets	46,500	[1]	10,268	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Warrant Liability
Fair value of financial assets and liabilities
Total financial liabilities	0		0
Significant Other Observable Inputs (Level 2)
Fair value of financial assets and liabilities
Total financial assets	0		0
Total financial liabilities	0		0
Significant Other Observable Inputs (Level 2) | Money Market Funds
Fair value of financial assets and liabilities
Total financial assets	0	[1]	0	[1]
Significant Other Observable Inputs (Level 2) | Warrant Liability
Fair value of financial assets and liabilities
Total financial liabilities	0		0
Significant Unobservable Inputs (Level 3)
Fair value of financial assets and liabilities
Total financial assets	0		0
Total financial liabilities	10,290		5,903
Significant Unobservable Inputs (Level 3) | Money Market Funds
Fair value of financial assets and liabilities
Total financial assets	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) | Warrant Liability
Fair value of financial assets and liabilities
Total financial liabilities	$ 10,290		$ 5,903

[1] Included in cash and cash equivalents on the Company's condensed consolidated balance sheets.