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Quarterly Financial Data - Schedule of Quarterly Financial Information (Parenthetical) (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Apr. 25, 2018
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Schedule Of Quarterly Financial Data [Line Items]                        
Recovery from a settlement with a vendor   $ 4,419                    
Gross profit (loss)   12,411 $ (9,742) $ 3,073 $ 10,093 $ (10,204) $ (7,285) $ 11,340 $ 11,615 $ 15,835 $ 5,466 $ (49,306)
Net income (loss)   (13,045) (26,084) (27,506) (5,591) 914 (17,112) (7,033) (5,986) (72,226) (29,217) 112,168
Loss on extinguishment of debt     (5,951)             (5,951)   (8,703)
Interest expense, net $ (900) (11,056) (11,009) (11,693) (9,306) (9,326) (9,291) (9,292) (9,358) (43,064) (37,267) (30,945)
Severance benefits and accelerated stock-based compensation   (5,300)                    
Provision (benefit) for income taxes   (764) 2,426 (4,324) 922 30,018 6,698 2,761 $ 1,282 $ 1,740 $ (40,759) $ (41,956)
Income From Discontinued Operations Net of Taxes [Member]                        
Schedule Of Quarterly Financial Data [Line Items]                        
Net income (loss)           1,076            
Turnaround Expense [Member]                        
Schedule Of Quarterly Financial Data [Line Items]                        
Gross profit (loss)   (116) (7,939) (1,412) (302) (102) (1,098) (120)        
Net income (loss)   $ (116) $ (7,939) $ (1,412) $ (302) $ (102) $ (1,098) (120)        
Recovery of Precious Metals [Member]                        
Schedule Of Quarterly Financial Data [Line Items]                        
Recovery of precious metals               $ 2,905