Shares of Class A Common Stock for Future Issuance (Detail)	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Stockholders Equity [Line Items]
Stock options under the our incentive plans	2,295,210	1,825,320
Warrants outstanding	6,670,103
Total shares reserved for future issuance	8,965,313
Stock Options
Schedule Of Stockholders Equity [Line Items]
Stock options under the our incentive plans	1,995,210
Equity Compensation Plans Not Approved by Security Holders
Schedule Of Stockholders Equity [Line Items]
Total shares reserved for future issuance	300,000