XML 80 R68.htm IDEA: XBRL DOCUMENT v3.21.1
Fair value measurements (Details 4) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Fair value, balance sheet grouping [Line Items]      
Long-term debt $ 2,253,274 $ 2,213,130 $ 2,455,235
Carrying amount      
Fair value, balance sheet grouping [Line Items]      
Long-term debt 2,253,274 2,213,130 2,455,235
Fair value      
Fair value, balance sheet grouping [Line Items]      
Long-term debt, fair value $ 2,473,806 $ 2,537,289 $ 2,618,297