Summary of Significant Accounting Policies - Warrants and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended		24 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019
Warrants
Warrant, equity component	$ 3,448
Assets:
Cash & cash equivalents	3,891	$ 16,284	$ 3,891
Total assets	3,891	16,284	3,891
Liabilities:
Warrant liability		3,448
Total liabilities		3,448
Fair value measurements of the warrant liability
Beginning Balance	3,448	11,862	11,862
Exercise of warrants	(3,448)	(1,130)
Change in fair value of warrant liability		(7,284)
Warrant, equity component	$ 3,448
Ending Balance		$ 3,448
Expected dividend yield (as a percentage)	0.00%	0.00%
Level 1
Assets:
Cash & cash equivalents	$ 3,891	$ 16,284	3,891
Total assets	$ 3,891	16,284	$ 3,891
Level 3
Liabilities:
Warrant liability		3,448
Total liabilities		$ 3,448