Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Outstanding Shares of Potentially Dilutive Securities Excluded from Calculation of Dilutive Net Loss per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares of potentially dilutive securities (in shares)	43,258	33,326	35,593
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares of potentially dilutive securities (in shares)	12,707	11,901	13,740
Shares of common stock to be issued upon conversion of Series A Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares of potentially dilutive securities (in shares)	13,375	0	0
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares of potentially dilutive securities (in shares)	1,274	1,884	1,812
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares of potentially dilutive securities (in shares)	750	750	1,250
Shares of common stock to be issued upon conversion of the Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares of potentially dilutive securities (in shares)	15,152	18,791	18,791