Historical Outstanding Anti Dilutive Securities not Included in Diluted Net Loss Per Share Calculation (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrants/ options outstanding	55,910	30,488	55,910	52,488
2013 Convertible Senior Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrants/ options outstanding	370	1,404	370	1,404
2016 Convertible Senior Secured Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrants/ options outstanding	22,000		22,000	22,000
2017 Exchange Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrants/ options outstanding	2,696		2,696
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrants/ options outstanding	22,500	22,500	22,500	22,500
Stock Options and PSU's
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrants/ options outstanding	8,344	6,584	8,344	6,584