Commitments and Contingencies Commitments And Contingencies - Gross Future Minimum Volume Charges (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Commitments and Contingencies - Gross Future Minimum Volume Charges [Abstract]
2019	$ 8,275
2020	2,167
2021	1,997
Thereafter	0
Total	$ 12,439