Preferred and Common Stock (Tables)
12 Months Ended
Dec. 31, 2014
Stockholders' Equity Note [Abstract]  
Common Stock, Capital Shares reserved for future issuance
Common shares reserved for future issuance upon the exercise, issuance or conversion of the respective equity instruments at December 31, 2014 are as follows (in thousands):
Stock options:
 
  Issued and outstanding
11,116

  Available for future grant
8,611

Issued and outstanding restricted stock units
1,674

Available for issuance under the ESPP
1,388

Warrants outstanding
250

Convertible Senior Notes
28,088

Total
51,127