Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Feb. 16, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 121,686	$ 115,840
Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 121,686	$ 115,691
4.50% Exchangeable Senior Notes Due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate	4.50%	4.50%	4.50%
4.50% Exchangeable Senior Notes Due 2023 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 143,750	$ 143,750
Long-term debt, fair value	$ 107,692