Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 81,830	$ 69,886
Marketable Securities	43,873	91,015
Cash
Assets
Cash and cash equivalents	55,796	34,726
Money market funds
Assets
Cash and cash equivalents	26,034	35,160
Domestic corporate debt securities
Assets
Marketable Securities	38,910	41,229
Domestic corporate commercial paper
Assets
Marketable Securities	4,963	24,905
Agency bonds
Assets
Marketable Securities		12,389
US treasury bonds
Assets
Marketable Securities		12,492
Recurring basis
Assets
Cash and cash equivalents	81,830	69,886
Marketable Securities	43,873	91,015
Recurring basis | Cash
Assets
Cash and cash equivalents	55,796	34,726
Recurring basis | Money market funds
Assets
Cash and cash equivalents	26,034	35,160
Recurring basis | Domestic corporate debt securities
Assets
Marketable Securities	38,910	41,229
Recurring basis | Domestic corporate commercial paper
Assets
Marketable Securities	4,963	24,905
Recurring basis | Agency bonds
Assets
Marketable Securities		12,389
Recurring basis | US treasury bonds
Assets
Marketable Securities		12,492
Recurring basis | Level 1
Assets
Cash and cash equivalents	81,830	69,886
Marketable Securities	0	0
Recurring basis | Level 1 | Cash
Assets
Cash and cash equivalents	55,796	34,726
Recurring basis | Level 1 | Money market funds
Assets
Cash and cash equivalents	26,034	35,160
Recurring basis | Level 1 | Domestic corporate debt securities
Assets
Marketable Securities	0	0
Recurring basis | Level 1 | Domestic corporate commercial paper
Assets
Marketable Securities	0	0
Recurring basis | Level 1 | Agency bonds
Assets
Marketable Securities		0
Recurring basis | Level 1 | US treasury bonds
Assets
Marketable Securities		0
Recurring basis | Level 2
Assets
Cash and cash equivalents	0	0
Marketable Securities	43,873	91,015
Recurring basis | Level 2 | Cash
Assets
Cash and cash equivalents	0	0
Recurring basis | Level 2 | Money market funds
Assets
Cash and cash equivalents	0	0
Recurring basis | Level 2 | Domestic corporate debt securities
Assets
Marketable Securities	38,910	41,229
Recurring basis | Level 2 | Domestic corporate commercial paper
Assets
Marketable Securities	4,963	24,905
Recurring basis | Level 2 | Agency bonds
Assets
Marketable Securities		12,389
Recurring basis | Level 2 | US treasury bonds
Assets
Marketable Securities		12,492
Recurring basis | Level 3
Assets
Cash and cash equivalents	0	0
Marketable Securities	0	0
Recurring basis | Level 3 | Cash
Assets
Cash and cash equivalents	0	0
Recurring basis | Level 3 | Money market funds
Assets
Cash and cash equivalents	0	0
Recurring basis | Level 3 | Domestic corporate debt securities
Assets
Marketable Securities	0	0
Recurring basis | Level 3 | Domestic corporate commercial paper
Assets
Marketable Securities	$ 0	0
Recurring basis | Level 3 | Agency bonds
Assets
Marketable Securities		0
Recurring basis | Level 3 | US treasury bonds
Assets
Marketable Securities		$ 0