Fair Value Measurements - Summary of Fair Value Measurements of Company's Financial Assets and Liabilities (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Assets at fair value	$ 222,066	$ 244,388
Liabilities:
Derivative liability	1,051	969
Level 1 [Member]
Assets:
Assets at fair value	104,776	147,208
Level 2 [Member]
Assets:
Assets at fair value	117,290	97,180
Level 3 [Member]
Liabilities:
Derivative liability	1,051	969
Derivative Liability Exit Fee [Member]
Liabilities:
Derivative liability	1,051	969
Derivative Liability Exit Fee [Member] | Level 3 [Member]
Liabilities:
Derivative liability	1,051	969
Money Market Funds [Member]
Assets:
Assets at fair value	100,755	147,208
Money Market Funds [Member] | Level 1 [Member]
Assets:
Assets at fair value	100,755	147,208
Commercial Paper [Member]
Assets:
Assets at fair value	57,710	56,041
Commercial Paper [Member] | Level 2 [Member]
Assets:
Assets at fair value	57,710	56,041
Corporate Bonds [Member]
Assets:
Assets at fair value	49,122	33,134
Corporate Bonds [Member] | Level 2 [Member]
Assets:
Assets at fair value	49,122	33,134
Asset-Backed Securities [Member]
Assets:
Assets at fair value	10,458	8,005
Asset-Backed Securities [Member] | Level 2 [Member]
Assets:
Assets at fair value	10,458	$ 8,005
U.S. Treasury Notes [Member]
Assets:
Assets at fair value	4,021
U.S. Treasury Notes [Member] | Level 1 [Member]
Assets:
Assets at fair value	$ 4,021