Long-term Debt - Principal Amount of Debt and Associated Paid-in Kind Interest Payable by Year of Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Sep. 06, 2016
Debt Instrument [Line Items]
2018, Principal and paid-in kind interest payable	$ 0
2019, Principal and paid-in kind interest payable	307,973
2020, Principal and paid-in kind interest payable	892,739
2021, Principal and paid-in kind interest payable	0
2022, Principal and paid-in kind interest payable	0
Thereafter, Principal and paid-in kind interest payable	0
Total, Principal and paid-in kind interest payable	1,200,712
10% Senior Secured Toggle Notes due 2020
Debt Instrument [Line Items]
2018, Principal	0
2019, Principal	0
2020, Principal	697,195
2021, Principal	0
2022, Principal	0
Thereafter, Principal	0
Long term debt principal amount	697,195	$ 697,195
7¾% Convertible Second Lien PIK Notes due 2019
Debt Instrument [Line Items]
Long term debt principal amount	284,442	268,432
2018, Principal and paid-in kind interest payable	0
2019, Principal and paid-in kind interest payable	290,014
2020, Principal and paid-in kind interest payable	0
2021, Principal and paid-in kind interest payable	0
2022, Principal and paid-in kind interest payable	0
Thereafter, Principal and paid-in kind interest payable	0
Total, Principal and paid-in kind interest payable	290,014
9½% Convertible Second Lien PIK Notes due 2020
Debt Instrument [Line Items]
Long term debt principal amount	187,062	174,182
2018, Principal and paid-in kind interest payable	0
2019, Principal and paid-in kind interest payable	0
2020, Principal and paid-in kind interest payable	187,879
2021, Principal and paid-in kind interest payable	0
2022, Principal and paid-in kind interest payable	0
Thereafter, Principal and paid-in kind interest payable	0
Total, Principal and paid-in kind interest payable	187,879
10% Senior Notes due 2020
Debt Instrument [Line Items]
2018, Principal	0
2019, Principal	0
2020, Principal	2,805
2021, Principal	0
2022, Principal	0
Thereafter, Principal	0
Long term debt principal amount	2,805	2,805
7¾% Senior Notes due 2019
Debt Instrument [Line Items]
2018, Principal	0
2019, Principal	17,959
2020, Principal	0
2021, Principal	0
2022, Principal	0
Thereafter, Principal	0
Long term debt principal amount	17,959	17,959	$ 18,000
9½% Senior Notes due 2020
Debt Instrument [Line Items]
2018, Principal	0
2019, Principal	0
2020, Principal	4,860
2021, Principal	0
2022, Principal	0
Thereafter, Principal	0
Long term debt principal amount	$ 4,860	$ 4,860	$ 4,900