Fair Value Measurement - Narrative (Details) - Senior Notes - 4.50% Exchangeable Senior Notes Due 2023 - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 143,750	$ 143,750
Estimated fair value of long-term debt	$ 147,523

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant