XML 171 R89.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Fair value measurements (Details 5) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt $ 2,243,107 $ 2,108,695
Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt 2,243,107 2,108,695
Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, fair value $ 2,418,631 $ 2,183,819