Fair Value Measurements - Summary of Fair Value Measurements of Company's Financial Assets and Liabilities (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Assets at fair value	$ 203,757	$ 244,388
Liabilities:
Derivative liability	1,121	969
Level 1 [Member]
Assets:
Assets at fair value	111,493	147,208
Level 2 [Member]
Assets:
Assets at fair value	92,264	97,180
Level 3 [Member]
Liabilities:
Derivative liability	1,121	969
Derivative Liability Exit Fee [Member]
Liabilities:
Derivative liability	1,121	969
Derivative Liability Exit Fee [Member] | Level 3 [Member]
Liabilities:
Derivative liability	1,121	969
Money Market Funds [Member]
Assets:
Assets at fair value	99,410	147,208
Money Market Funds [Member] | Level 1 [Member]
Assets:
Assets at fair value	99,410	147,208
Commercial Paper [Member]
Assets:
Assets at fair value	46,443	56,041
Commercial Paper [Member] | Level 2 [Member]
Assets:
Assets at fair value	46,443	56,041
Corporate Bonds [Member]
Assets:
Assets at fair value	35,289	33,134
Corporate Bonds [Member] | Level 2 [Member]
Assets:
Assets at fair value	35,289	33,134
Asset-Backed Securities [Member]
Assets:
Assets at fair value	10,532	8,005
Asset-Backed Securities [Member] | Level 2 [Member]
Assets:
Assets at fair value	10,532	$ 8,005
U.S. Treasury Notes [Member]
Assets:
Assets at fair value	4,008
U.S. Treasury Notes [Member] | Level 1 [Member]
Assets:
Assets at fair value	4,008
US Government Agencies Short-term Debt Securities [Member]
Assets:
Assets at fair value	8,075
US Government Agencies Short-term Debt Securities [Member] | Level 1 [Member]
Assets:
Assets at fair value	$ 8,075