Fair Value Measurements - Fair Value and Carrying Value (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Jul. 03, 2013	Aug. 19, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face Value	$ 272,629,000	$ 280,295,000
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	206,023,000	211,894,000
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	281,398,000	286,396,000
Senior Notes | 2017 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face Value	0	22,650,000	$ 200,000,000	$ 150,000,000
Senior Notes | 2017 Notes | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	0	21,970,000
Senior Notes | 2017 Notes | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	0	22,568,000
Senior Notes | 2021 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face Value	9,427,000	14,177,000
Senior Notes | 2021 Notes | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	7,306,000	12,192,000
Senior Notes | 2021 Notes | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	9,821,000	15,228,000
Payment in Kind (PIK) Note | 2021 PIK Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face Value	263,202,000	243,468,000
Payment in Kind (PIK) Note | 2021 PIK Notes | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	198,717,000	177,732,000
Payment in Kind (PIK) Note | 2021 PIK Notes | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 271,577,000	$ 248,600,000