XML 150 R127.htm IDEA: XBRL DOCUMENT v3.19.1
Financial instruments (Details 18) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Single series bond Three [Member] | Interest payment [Member]      
Financial instruments [Line Items]      
Repayments of bonds, notes and debentures $ 10,875 $ 10,875 $ 10,875