Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued capital costs	$ 13,603	$ 33,105
Accrued operating expenses	11,965	12,149
Other accrued liabilities	831	4,956
Total accrued liabilities	$ 26,399	$ 50,210