Fair Value Measurements - Carrying Value and Fair Value of Long-Term Debt and Other Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Reported Value Measurement | Warrant
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Warrants not settleable in cash, fair value	$ 5,007	$ 6,808
Reported Value Measurement | 5% Convertible Senior Notes due 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	100,411	95,486
Reported Value Measurement | 7.75% Senior Secured Note due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	290,763	289,326
Reported Value Measurement | Mid Pac Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	1,466
Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement | 5% Convertible Senior Notes due 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	121,488	149,007
Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement | 7.75% Senior Secured Note due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	270,000	300,423
Fair Value, Inputs, Level 3 | Estimate of Fair Value Measurement | Warrant
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Warrants not settleable in cash, fair value	5,007	$ 6,808
Fair Value, Inputs, Level 3 | Estimate of Fair Value Measurement | Mid Pac Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 1,466