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Long-Term Debt - 8.750% Senior Notes - Additional Information (Details) - USD ($)
3 Months Ended 12 Months Ended
Jan. 04, 2018
Apr. 15, 2016
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Sep. 30, 2019
Jan. 31, 2018
Debt Instrument [Line Items]              
Gain (loss) on extinguishment of debt       $ 0 $ (8,620,000)    
8.750% Senior Notes Due April 15, 2019              
Debt Instrument [Line Items]              
Debt instrument interest rate (as a percent)       8.75% 8.75% 8.75% 8.75%
Debt instrument maturity date       Apr. 15, 2019      
Redemption price, percentage   104.375%          
Debt instrument redemption price amount excludes accrued interest   $ 158,500,000          
11.25% Senior Notes              
Debt Instrument [Line Items]              
Debt instrument face amount             $ 250,000,000
Debt instrument interest rate (as a percent)       11.25%     11.25%
Redemption price, percentage 111.25%            
Unsecured Debt | 8.750% Senior Notes Due April 15, 2019              
Debt Instrument [Line Items]              
Gain (loss) on extinguishment of debt     $ (8,600,000)