STOCK-BASED COMPENSATION (Details) (USD $) | 0 Months Ended | 3 Months Ended |
Mar. 31, 2015 | Dec. 31, 2014 | Mar. 31, 2015 | Mar. 31, 2014 |
Aggregate Intrinsic Value | | | | |
Outstanding at the end of the period | $1,188,678,000 | | $1,188,678,000 | |
Exercisable at end of period | 3,448,000 | | 3,448,000 | |
Service-based stock options | | | | |
Stock-Based Compensation | | | | |
Vesting period | | | 4 years | |
Expiration period | | | 10 years | |
Grant date fair value | | | | $2.55 |
Net compensation expense related to employees and directors (in dollars) | | | 900,000 | 300,000 |
Weighted average assumptions used to estimate fair value of each service-based stock option grant | | | | |
Expected dividend rate (as a percent) | | | 0.00% | |
Options | | | | |
Outstanding at the beginning of the period (in shares) | 2,392,988 | 477,530 | 477,530 | |
Granted (in shares) | | | 1,949,100 | |
Exercised (in shares) | | | 0 | |
Expired (in shares) | | | -4,392 | |
Forfeited (in shares) | | | -29,250 | |
Outstanding at the end of the period (in shares) | 2,392,988 | | 2,392,988 | |
Exercisable at the end of the period (in shares) | 249,627 | | 249,627 | |
Weighted Average Exercise Price | | | | |
Outstanding at the beginning of the period (in dollars per share) | $6.73 | $21.74 | $21.74 | |
Granted (in dollars per share) | | | $2.22 | |
Exercised (in dollars per share) | | | $0 | |
Expired (in dollars per share) | | | $48.27 | |
Forfeited (in dollars per share) | | | $3.02 | |
Outstanding at the end of the period (in dollars per share) | $6.73 | | $6.73 | |
Exercisable at the end of the period (in dollars per share) | $31.57 | | $31.57 | |
Weighted Average Remaining Contractual Term (Years) | | | | |
Outstanding at the beginning of the period | 9 years 4 months 28 days | 8 years 0 months 15 days | | |
Outstanding at the end of the period | 9 years 4 months 28 days | 8 years 0 months 15 days | | |
Exercisable at the end of the period | 7 years 2 months 23 days | | | |
Additional disclosures | | | | |
Total unrecognized compensation cost (in dollars) | 4,200,000 | | 4,200,000 | |
Weighted average period over which unrecognized compensation is expected to be recognized (in years) | | | 3 years 6 months | |
Total fair value of options vested (in dollars) | | | $300,000 | $700,000 |
Service-based stock options | Minimum | | | | |
Weighted average assumptions used to estimate fair value of each service-based stock option grant | | | | |
Expected stock price volatility (as a percent) | | | 80.30% | 82.40% |
Risk-free interest rate (as a percent) | | | 1.50% | 2.10% |
Expected life (in years) | | | 5 years 6 months | 6 years 1 month 5 days |
Service-based stock options | Maximum | | | | |
Weighted average assumptions used to estimate fair value of each service-based stock option grant | | | | |
Expected stock price volatility (as a percent) | | | 88.10% | 83.30% |
Risk-free interest rate (as a percent) | | | 1.90% | 2.20% |
Expected life (in years) | | | 6 years 3 months 18 days | 6 years 3 months 18 days |