Inventory - Components of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Inventory
Equipment and materials	$ 19,563	$ 25,103
Crude oil inventory	8,746	8,826
Total inventory	28,309	33,929
Long-term inventory
Linefill in third party pipelines	17,510	14,522
Total long-term inventory	17,510	14,522
Total	$ 45,819	$ 48,451