Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 128,210	$ 121,686
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% Exchangeable Senior Notes Due 2023 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, gross	$ 143,750	$ 143,750