Long-Term Debt - Tabular Disclosure (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Long-Term Debt
Total principal amount	$ 714,148	$ 737,148
Less: unamortized discount	(5,987)	(6,240)
Less: debt issuance costs, net	(6,575)	(6,899)
Total carrying amount	701,586	724,009
2022 Notes | Senior notes
Long-Term Debt
Total principal amount	409,148	409,148
2023 Notes | Senior notes
Long-Term Debt
Total principal amount	150,000	150,000
Revolving credit facility | Wells Fargo Bank N.A. | Revolver | Line of credit
Long-Term Debt
Total principal amount	$ 155,000	$ 178,000