Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Fair Value Measurements Fair Value Measurements (Estimated Fair Value of Other Financial Assets and Liabilities) (Details)
$ in Thousands
Mar. 31, 2019
USD ($)
3.0% Convertible Senior Notes  
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Debt instrument, interest rate, stated percentage 3.00%
3.25% Convertible Senior Notes  
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Debt instrument, interest rate, stated percentage 3.25%
Convertible Debt | 3.0% Convertible Senior Notes  
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Debt instrument, interest rate, stated percentage 3.00%
Convertible Debt | 3.25% Convertible Senior Notes  
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Debt instrument, interest rate, stated percentage 3.25%
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) $ 2,027
Investments, at cost, in 50% or less owned companies (included in other assets) 4,300
Long-term debt, including current portion 323,611
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
Long-term debt, including current portion 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) 2,020
Long-term debt, including current portion 335,144
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
Long-term debt, including current portion $ 0