Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Estimated Fair Value of Other Financial Assets and Liabilities) (Details)

v3.20.4
Fair Value Measurements (Estimated Fair Value of Other Financial Assets and Liabilities) (Details) - USD ($)
$ in Thousands
Feb. 25, 2021
Dec. 31, 2020
Dec. 31, 2019
Subsequent Event      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Proceeds from sale of investment, at cost, in 50% or less owned companies $ 5,000    
Gain on sale of investment, at cost, in 50% or less owned companies $ 1,500    
Reported Value Measurement      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notes receivable from third parties (included in other receivables and other assets)   $ 3,158 $ 1,119
Investments, at cost, in 50% or less owned companies (included in other assets)   4,201 4,201
Long-term debt, including current portion   277,044 314,466
Estimate of Fair Value Measurement | Level 1      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notes receivable from third parties (included in other receivables and other assets)   0 0
Long-term debt, including current portion   0 0
Estimate of Fair Value Measurement | Level 2      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notes receivable from third parties (included in other receivables and other assets)   3,159 1,082
Long-term debt, including current portion   295,066 330,088
Estimate of Fair Value Measurement | Level 3      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notes receivable from third parties (included in other receivables and other assets)   0 0
Long-term debt, including current portion   $ 0 $ 0