Operating Leases - Balance Sheet Presentation (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Right-of Use Assets:
Right-of-use assets	$ 322	$ 574
Right-of-use assets, balance sheet line item	Other assets	Other assets
Operating Lease Liabilities:
Operating lease liabilities, current	$ 297	$ 370
Operating lease liabilities, noncurrent	53	254
Operating lease liabilities	$ 350	$ 624
Operating lease liabilities, current, balance sheet line item	Accrued liabilities	Accrued liabilities
Operating lease liabilities, noncurrent, balance sheet line item	Other long-term liabilities	Other long-term liabilities