Annual report pursuant to Section 13 and 15(d)

Assets and Liabilities Held for Sale - Additional Information (Details)

v3.19.1
Assets and Liabilities Held for Sale - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Mar. 31, 2019
Mar. 31, 2018
Discontinued Operations And Disposal Groups [Abstract]          
Impairment loss $ 6,449 $ 0 $ 14,816 $ 6,449 $ 14,816