Fair Value Measurements - Summary of Estimated Fair Value of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 1,447,421	$ 1,368,500
10.75% first lien notes due 2021
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, fair value	482,250
7.75% second lien notes due 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, fair value	327,449
2.625% convertible senior notes due 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, fair value	305,378	791,209
3.125% convertible senior notes due 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 332,344	$ 577,291