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Fair Value Measurements - Estimated Fair Value of Financial Instruments (Details) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Carrying Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cost method investment $ 552 $ 552
Highview Obligation 208 220
Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cost method investment 552 552
Highview Obligation $ 208 $ 220