Revenue From Contracts with Customers - Disaggregate Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue, Initial Application Period Cumulative Effect Transition
Total Revenues	$ 318,646	$ 474,994
By-products and other
Revenue, Initial Application Period Cumulative Effect Transition
Total Revenues	11,449	31,658
Graphite Electrodes - Three-to-five-year take-or-pay contracts
Revenue, Initial Application Period Cumulative Effect Transition
Total Revenues	276,379	396,040
Graphite Electrodes - Short-term agreements and spot sales
Revenue, Initial Application Period Cumulative Effect Transition
Total Revenues	$ 30,818	$ 47,296