Commitments and Contingencies - Long-Term Fixed Supplier Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Years ended, December 31:
2017	$ 16,786
2018	11,536
2019	3,312
Total	31,634
Annual fixed fees incurred	$ 23,000	$ 12,800	$ 9,300