Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents and restricted cash reported within the condensed balance sheets
Cash and cash equivalents	$ 157,954,000	$ 114,504,000
Restricted cash	1,282,000	0
Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows	$ 159,236,000	114,504,000	$ 8,242,000
Convertible Preferred Stock Warrants
Warrants to purchase (in shares)	49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	$ 503,000
Prepaid expenses and other current assets
Other Income
Receivables under service agreements	237,000	282,000
Other current liabilities
Other Income
Contract liabilities	$ 0	$ 200,000