Cumulative Effect on Balance Sheets of Reclassification Attributed to Adoption of Standard (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2008
Class of Warrant or Right [Line Items]
Liabilities Warrants	$ 11,776	$ 12,962	$ 72
Stockholders' Equity, Warrants			18,866
Stockholders' Equity, Deficit Accumulated During the Development Stage	340,831	283,724	(83,495)
As reported
Class of Warrant or Right [Line Items]
Stockholders' Equity, Warrants			20,504
Stockholders' Equity, Deficit Accumulated During the Development Stage			(85,061)
Restatement Adjustment
Class of Warrant or Right [Line Items]
Liabilities Warrants			72
Stockholders' Equity, Warrants			(1,638)
Stockholders' Equity, Deficit Accumulated During the Development Stage			$ 1,566