Commitments and Contingencies Commitments and Contingencies - Gross Future Minimum Volume Charges (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies - Gross Future Minimum Volume Charges [Abstract]
2019	$ 10,049
2020	2,167
2021	1,996
Thereafter	0
Total	$ 14,212