Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 40,723	$ 69,886
Marketable Securities	97,257	91,015
Domestic corporate debt securities
Assets
Marketable Securities	67,477	41,229
Domestic corporate commercial paper
Assets
Marketable Securities	17,361	24,905
Agency bonds
Assets
Marketable Securities	12,419	12,389
US treasury bonds
Assets
Marketable Securities		12,492
Cash
Assets
Cash and cash equivalents	21,949	34,726
Money market funds
Assets
Cash and cash equivalents	18,774	35,160
Recurring basis
Assets
Cash and cash equivalents	40,723	69,886
Marketable Securities	97,257	91,015
Recurring basis | Domestic corporate debt securities
Assets
Marketable Securities	67,477	41,229
Recurring basis | Domestic corporate commercial paper
Assets
Marketable Securities	17,361	24,905
Recurring basis | Agency bonds
Assets
Marketable Securities	12,419	12,389
Recurring basis | US treasury bonds
Assets
Marketable Securities		12,492
Recurring basis | Cash
Assets
Cash and cash equivalents	21,949	34,726
Recurring basis | Money market funds
Assets
Cash and cash equivalents	18,774	35,160
Recurring basis | Level 1
Assets
Cash and cash equivalents	40,723	69,886
Marketable Securities	0	0
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	0
Recurring basis | Level 1 | US treasury bonds
Assets
Marketable Securities		0
Recurring basis | Level 1 | Cash
Assets
Cash and cash equivalents	21,949	34,726
Recurring basis | Level 1 | Money market funds
Assets
Cash and cash equivalents	18,774	35,160
Recurring basis | Level 2
Assets
Cash and cash equivalents	0	0
Marketable Securities	97,257	91,015
Recurring basis | Level 2 | Domestic corporate debt securities
Assets
Marketable Securities	67,477	41,229
Recurring basis | Level 2 | Domestic corporate commercial paper
Assets
Marketable Securities	17,361	24,905
Recurring basis | Level 2 | Agency bonds
Assets
Marketable Securities	12,419	12,389
Recurring basis | Level 2 | US treasury bonds
Assets
Marketable Securities		12,492
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 3
Assets
Cash and cash equivalents	0	0
Marketable Securities	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	0
Recurring basis | Level 3 | US treasury bonds
Assets
Marketable Securities		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