Net Income (Loss) Per Share - Warrants, Options and Purchase Rights Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	8,300	8,300	8,300	8,300
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	10,542	11,635	10,732	11,635
2004 Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	21	42	21	42