Summary of Significant Accounting Policies - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Nov. 14, 2017
Assets:
Cash equivalents	$ 34,826	$ 25,737
Total assets	34,826	25,737
Liabilities:
Warrant liability	16,713	11,862	$ 14,344
Total liabilities	$ 16,713	11,862
Fair value measurements of the warrant liability
Expected dividend yield	0.00%
Level 1
Assets:
Cash equivalents	$ 34,826	25,737
Total assets	34,826	25,737
Level 3
Liabilities:
Warrant liability	16,713	11,862
Total liabilities	16,713	$ 11,862
Recurring | Warrant Liability
Fair value measurements of the warrant liability
Beginning Balance	11,862
Loss (gain) on change in fair value	4,851
Ending Balance	$ 16,713